#!/usr/bin/env python3
# Copyright 2011 The Emscripten Authors.  All rights reserved.
# Emscripten is available under two separate licenses, the MIT license and the
# University of Illinois/NCSA Open Source License.  Both these licenses can be
# found in the LICENSE file.

"""emcc - compiler helper script
=============================

emcc is a drop-in replacement for a compiler like gcc or clang.

See  emcc --help  for details.

emcc can be influenced by a few environment variables:

  EMCC_DEBUG - "1" will log out useful information during compilation, as well as
               save each compiler step as an emcc-* file in the temp dir
               (by default /tmp/emscripten_temp). "2" will save additional emcc-*
               steps, that would normally not be separately produced (so this
               slows down compilation).

  EMMAKEN_NO_SDK - Will tell emcc *not* to use the emscripten headers. Instead
                   your system headers will be used.
"""

from __future__ import print_function

import json
import logging
import os
import re
import shlex
import stat
import sys
import time
import base64
from subprocess import PIPE

import emscripten
from tools import shared, system_libs
from tools import colored_logger, diagnostics, building
from tools.shared import unsuffixed, unsuffixed_basename, WINDOWS, safe_move, safe_copy
from tools.shared import run_process, asbytes, read_and_preprocess, exit_with_error, DEBUG
from tools.response_file import substitute_response_files
from tools.minimal_runtime_shell import generate_minimal_runtime_html
import tools.line_endings
from tools.toolchain_profiler import ToolchainProfiler
from tools import js_manipulation
from tools import wasm2c
from tools import webassembly

if __name__ == '__main__':
  ToolchainProfiler.record_process_start()

try:
  from urllib.parse import quote
except ImportError:
  # Python 2 compatibility
  from urllib import quote

logger = logging.getLogger('emcc')

# endings = dot + a suffix, safe to test by  filename.endswith(endings)
C_ENDINGS = ('.c', '.i')
CXX_ENDINGS = ('.cpp', '.cxx', '.cc', '.c++', '.CPP', '.CXX', '.C', '.CC', '.C++', '.ii')
OBJC_ENDINGS = ('.m', '.mi')
OBJCXX_ENDINGS = ('.mm', '.mii')
ASSEMBLY_CPP_ENDINGS = ('.S',)
SPECIAL_ENDINGLESS_FILENAMES = (os.devnull,)

SOURCE_ENDINGS = C_ENDINGS + CXX_ENDINGS + OBJC_ENDINGS + OBJCXX_ENDINGS + SPECIAL_ENDINGLESS_FILENAMES + ASSEMBLY_CPP_ENDINGS
C_ENDINGS = C_ENDINGS + SPECIAL_ENDINGLESS_FILENAMES # consider the special endingless filenames like /dev/null to be C

JS_ENDINGS = ('.js', '.mjs', '.out', '')
WASM_ENDINGS = ('.wasm',)
EXECUTABLE_ENDINGS = JS_ENDINGS + WASM_ENDINGS + ('.html',)
DYNAMICLIB_ENDINGS = ('.dylib', '.so') # Windows .dll suffix is not included in this list, since those are never linked to directly on the command line.
STATICLIB_ENDINGS = ('.a',)
ASSEMBLY_ENDINGS = ('.ll', '.s')
HEADER_ENDINGS = ('.h', '.hxx', '.hpp', '.hh', '.H', '.HXX', '.HPP', '.HH')

# Supported LLD flags which we will pass through to the linker.
SUPPORTED_LINKER_FLAGS = (
    '--start-group', '--end-group',
    '-(', '-)',
    '--whole-archive', '--no-whole-archive',
    '-whole-archive', '-no-whole-archive'
)

# Unsupported LLD flags which we will ignore.
# Maps to true if the flag takes an argument.
UNSUPPORTED_LLD_FLAGS = {
    # macOS-specific linker flag that libtool (ltmain.sh) will if macOS is detected.
    '-bind_at_load': False,
    # wasm-ld doesn't support map files yet.
    '--print-map': False,
    '-M': False,
    # wasm-ld doesn't support soname or other dynamic linking flags (yet).   Ignore them
    # in order to aid build systems that want to pass these flags.
    '-soname': True,
    '-allow-shlib-undefined': False,
    '-rpath': True,
    '-rpath-link': True,
    '-version-script': True,
}

LIB_PREFIXES = ('', 'lib')

DEFAULT_ASYNCIFY_IMPORTS = [
  'emscripten_sleep', 'emscripten_wget', 'emscripten_wget_data', 'emscripten_idb_load',
  'emscripten_idb_store', 'emscripten_idb_delete', 'emscripten_idb_exists',
  'emscripten_idb_load_blob', 'emscripten_idb_store_blob', 'SDL_Delay',
  'emscripten_scan_registers', 'emscripten_lazy_load_code',
  'emscripten_fiber_swap',
  'wasi_snapshot_preview1.fd_sync', '__wasi_fd_sync', '_emval_await']

# Mapping of emcc opt levels to llvm opt levels. We use llvm opt level 3 in emcc
# opt levels 2 and 3 (emcc 3 is unsafe opts, so unsuitable for the only level to
# get llvm opt level 3, and speed-wise emcc level 2 is already the slowest/most
# optimizing level)
LLVM_OPT_LEVEL = {
  0: ['-O0'],
  1: ['-O1'],
  2: ['-O3'],
  3: ['-O3'],
}

# Target options
final_js = None

UBSAN_SANITIZERS = {
  'alignment',
  'bool',
  'builtin',
  'bounds',
  'enum',
  'float-cast-overflow',
  'float-divide-by-zero',
  'function',
  'implicit-unsigned-integer-truncation',
  'implicit-signed-integer-truncation',
  'implicit-integer-sign-change',
  'integer-divide-by-zero',
  'nonnull-attribute',
  'null',
  'nullability-arg',
  'nullability-assign',
  'nullability-return',
  'object-size',
  'pointer-overflow',
  'return',
  'returns-nonnull-attribute',
  'shift',
  'signed-integer-overflow',
  'unreachable',
  'unsigned-integer-overflow',
  'vla-bound',
  'vptr',
  'undefined',
  'undefined-trap',
  'implicit-integer-truncation',
  'implicit-integer-arithmetic-value-change',
  'implicit-conversion',
  'integer',
  'nullability',
}


VALID_ENVIRONMENTS = ('web', 'webview', 'worker', 'node', 'shell')


# this function uses the global 'final' variable, which contains the current
# final output file. if a method alters final, and calls this method, then it
# must modify final globally (i.e. it can't receive final as a param and
# return it)
# TODO: refactor all this, a singleton that abstracts over the final output
#       and saving of intermediates
def save_intermediate(name, suffix='js'):
  if not DEBUG:
    return
  if not final_js:
    logger.debug('(not saving intermediate %s because not generating JS)' % name)
    return
  building.save_intermediate(final_js, name + '.' + suffix)


def save_intermediate_with_wasm(name, wasm_binary):
  if not DEBUG:
    return
  save_intermediate(name) # save the js
  building.save_intermediate(wasm_binary, name + '.wasm')


class TimeLogger(object):
  last = time.time()

  @staticmethod
  def update():
    TimeLogger.last = time.time()


def log_time(name):
  """Log out times for emcc stages"""
  if DEBUG:
    now = time.time()
    logger.debug('emcc step "%s" took %.2f seconds', name, now - TimeLogger.last)
    TimeLogger.update()


def base64_encode(b):
  b64 = base64.b64encode(b)
  if type(b64) == bytes:
    return b64.decode('ascii')
  else:
    return b64


class EmccOptions(object):
  def __init__(self):
    self.requested_debug = ''
    self.profiling = False
    self.profiling_funcs = False
    self.tracing = False
    self.emit_symbol_map = False
    self.llvm_opts = None
    self.use_closure_compiler = None
    self.closure_args = []
    self.js_transform = None
    self.pre_js = '' # before all js
    self.post_js = '' # after all js
    self.extern_pre_js = '' # before all js, external to optimized code
    self.extern_post_js = '' # after all js, external to optimized code
    self.preload_files = []
    self.embed_files = []
    self.exclude_files = []
    self.ignore_dynamic_linking = False
    self.shell_path = shared.path_from_root('src', 'shell.html')
    self.source_map_base = ''
    self.emrun = False
    self.cpu_profiler = False
    self.thread_profiler = False
    self.memory_profiler = False
    self.memory_init_file = None
    self.use_preload_cache = False
    self.use_preload_plugins = False
    self.proxy_to_worker = False
    self.default_object_extension = '.o'
    self.valid_abspaths = []
    self.cfi = False
    # Specifies the line ending format to use for all generated text files.
    # Defaults to using the native EOL on each platform (\r\n on Windows, \n on
    # Linux & MacOS)
    self.output_eol = os.linesep
    self.binaryen_passes = []
    self.no_entry = False
    self.shared = False
    self.relocatable = False


def use_source_map():
  return shared.Settings.DEBUG_LEVEL >= 4


def will_metadce():
  # The metadce JS parsing code does not currently support the JS that gets generated
  # when assertions are enabled.
  if shared.Settings.ASSERTIONS:
    return False
  return shared.Settings.OPT_LEVEL >= 3 or shared.Settings.SHRINK_LEVEL >= 1


def setup_environment_settings():
  # Environment setting based on user input
  environments = shared.Settings.ENVIRONMENT.split(',')
  if any([x for x in environments if x not in VALID_ENVIRONMENTS]):
    exit_with_error('Invalid environment specified in "ENVIRONMENT": ' + shared.Settings.ENVIRONMENT + '. Should be one of: ' + ','.join(VALID_ENVIRONMENTS))

  shared.Settings.ENVIRONMENT_MAY_BE_WEB = not shared.Settings.ENVIRONMENT or 'web' in environments
  shared.Settings.ENVIRONMENT_MAY_BE_WEBVIEW = not shared.Settings.ENVIRONMENT or 'webview' in environments
  shared.Settings.ENVIRONMENT_MAY_BE_NODE = not shared.Settings.ENVIRONMENT or 'node' in environments
  shared.Settings.ENVIRONMENT_MAY_BE_SHELL = not shared.Settings.ENVIRONMENT or 'shell' in environments

  # The worker case also includes Node.js workers when pthreads are
  # enabled and Node.js is one of the supported environments for the build to
  # run on. Node.js workers are detected as a combination of
  # ENVIRONMENT_IS_WORKER and ENVIRONMENT_IS_NODE.
  shared.Settings.ENVIRONMENT_MAY_BE_WORKER = \
      not shared.Settings.ENVIRONMENT or \
      'worker' in environments or \
      (shared.Settings.ENVIRONMENT_MAY_BE_NODE and shared.Settings.USE_PTHREADS)

  if not shared.Settings.ENVIRONMENT_MAY_BE_WORKER and shared.Settings.PROXY_TO_WORKER:
    exit_with_error('If you specify --proxy-to-worker and specify a "-s ENVIRONMENT=" directive, it must include "worker" as a target! (Try e.g. -s ENVIRONMENT=web,worker)')

  if not shared.Settings.ENVIRONMENT_MAY_BE_WORKER and shared.Settings.USE_PTHREADS:
    exit_with_error('When building with multithreading enabled and a "-s ENVIRONMENT=" directive is specified, it must include "worker" as a target! (Try e.g. -s ENVIRONMENT=web,worker)')


def minify_whitespace():
  return shared.Settings.OPT_LEVEL >= 2 and shared.Settings.DEBUG_LEVEL == 0


def embed_memfile():
  return (shared.Settings.SINGLE_FILE or
          (shared.Settings.MEM_INIT_METHOD == 0 and
           (not shared.Settings.MAIN_MODULE and
            not shared.Settings.SIDE_MODULE and
            not use_source_map())))


def expand_byte_size_suffixes(value):
  """Given a string with KB/MB size suffixes, such as "32MB", computes how
  many bytes that is and returns it as an integer.
  """
  value = value.strip()
  match = re.match(r'^(\d+)\s*([kmgt]?b)?$', value, re.I)
  if not match:
    exit_with_error("invalid byte size `%s`.  Valid suffixes are: kb, mb, gb, tb" % value)
  value, suffix = match.groups()
  value = int(value)
  if suffix:
    size_suffixes = {suffix: 1024 ** i for i, suffix in enumerate(['b', 'kb', 'mb', 'gb', 'tb'])}
    value *= size_suffixes[suffix.lower()]
  return value


def apply_settings(changes):
  """Take a list of settings in form `NAME=VALUE` and apply them to the global
  Settings object.
  """

  def standardize_setting_change(key, value):
    # boolean NO_X settings are aliases for X
    # (note that *non*-boolean setting values have special meanings,
    # and we can't just flip them, so leave them as-is to be
    # handled in a special way later)
    if key.startswith('NO_') and value in ('0', '1'):
      key = key[3:]
      value = str(1 - int(value))
    return key, value

  for change in changes:
    key, value = change.split('=', 1)
    key, value = standardize_setting_change(key, value)

    if key in shared.Settings.internal_settings:
      exit_with_error('%s is an internal setting and cannot be set from command line', key)

    # map legacy settings which have aliases to the new names
    # but keep the original key so errors are correctly reported via the `setattr` below
    user_key = key
    if key in shared.Settings.legacy_settings and key in shared.Settings.alt_names:
      key = shared.Settings.alt_names[key]

    # In those settings fields that represent amount of memory, translate suffixes to multiples of 1024.
    if key in ('TOTAL_STACK', 'INITIAL_MEMORY', 'MEMORY_GROWTH_LINEAR_STEP', 'MEMORY_GROWTH_GEOMETRIC_STEP',
               'GL_MAX_TEMP_BUFFER_SIZE', 'MAXIMUM_MEMORY', 'DEFAULT_PTHREAD_STACK_SIZE'):
      value = str(expand_byte_size_suffixes(value))

    if value and value[0] == '@':
      filename = value[1:]
      if not os.path.exists(filename):
        exit_with_error('%s: file not found parsing argument: %s' % (filename, change))
      value = open(filename).read()
    else:
      value = value.replace('\\', '\\\\')
    try:
      value = parse_value(value)
    except Exception as e:
      exit_with_error('a problem occurred in evaluating the content after a "-s", specifically "%s": %s', change, str(e))

    # Do some basic type checking by comparing to the existing settings.
    # Sadly we can't do this generically in the SettingsManager since there are settings
    # that so change types internally over time.
    existing = getattr(shared.Settings, user_key, None)
    if existing is not None:
      # We only currently worry about lists vs non-lists.
      if (type(existing) == list) != (type(value) == list):
        exit_with_error('setting `%s` expects `%s` but got `%s`' % (user_key, type(existing), type(value)))
    setattr(shared.Settings, user_key, value)

    if key == 'EXPORTED_FUNCTIONS':
      # used for warnings in emscripten.py
      shared.Settings.USER_EXPORTED_FUNCTIONS = shared.Settings.EXPORTED_FUNCTIONS[:]

    # TODO(sbc): Remove this legacy way.
    if key == 'WASM_OBJECT_FILES':
      shared.Settings.LTO = 0 if value else 'full'


def find_output_arg(args):
  """Find and remove any -o arguments.  The final one takes precedence.
  Return the final -o target along with the remaining (non-o) arguments.
  """
  outargs = []
  specified_target = None

  arg_count = len(args)
  i = 0

  while i < arg_count:
    arg = args[i]

    if arg == '-o':
      if i != arg_count - 1:
        specified_target = args[i + 1]
      i += 2
      continue

    if arg.startswith('-o'):
      specified_target = arg[2:]
      i += 1
      continue

    outargs.append(arg)

    if arg == '-mllvm' and i != arg_count - 1:
      # Explicitly skip over -mllvm arguments and their values because their
      # values could potentially start with -o and be confused for output file
      # specifiers.
      outargs.append(args[i + 1])
      i += 2
    else:
      i += 1

  return specified_target, outargs


def is_ar_file_with_missing_index(archive_file):
  # We parse the archive header outselves because llvm-nm --print-armap is slower and less
  # reliable.
  # See: https://github.com/emscripten-core/emscripten/issues/10195
  archive_header = b'!<arch>\n'
  file_header_size = 60

  with open(archive_file, 'rb') as f:
    header = f.read(len(archive_header))
    if header != archive_header:
      # This is not even an ar file
      return False
    file_header = f.read(file_header_size)
    if len(file_header) != file_header_size:
      # We don't have any file entires at all so we don't consider the index missing
      return False

  name = file_header[:16].strip()
  # If '/' is the name of the first file we have an index
  return name != b'/'


def ensure_archive_index(archive_file):
  # Fastcomp linking works without archive indexes.
  if not shared.Settings.AUTO_ARCHIVE_INDEXES:
    return
  if is_ar_file_with_missing_index(archive_file):
    diagnostics.warning('emcc', '%s: archive is missing an index; Use emar when creating libraries to ensure an index is created', archive_file)
    diagnostics.warning('emcc', '%s: adding index', archive_file)
    run_process([shared.LLVM_RANLIB, archive_file])


def get_all_js_syms(temp_files):
  # Runs the js compiler to generate a list of all symbols available in the JS
  # libraries.  This must be done separately for each linker invokation since the
  # list of symbols depends on what settings are used.
  # TODO(sbc): Find a way to optimize this.  Potentially we could add a super-set
  # mode of the js compiler that would generate a list of all possible symbols
  # that could be checked in.
  old_full = shared.Settings.INCLUDE_FULL_LIBRARY
  try:
    # Temporarily define INCLUDE_FULL_LIBRARY since we want a full list
    # of all available JS library functions.
    shared.Settings.INCLUDE_FULL_LIBRARY = True
    shared.Settings.ONLY_CALC_JS_SYMBOLS = True
    emscripten.generate_struct_info()
    glue, forwarded_data = emscripten.compile_settings(temp_files)
    forwarded_json = json.loads(forwarded_data)
    library_fns = forwarded_json['Functions']['libraryFunctions']
    library_fns_list = []
    for name in library_fns:
      if shared.is_c_symbol(name):
        name = shared.demangle_c_symbol_name(name)
        library_fns_list.append(name)
  finally:
    shared.Settings.ONLY_CALC_JS_SYMBOLS = False
    shared.Settings.INCLUDE_FULL_LIBRARY = old_full

  return library_fns_list


def filter_link_flags(flags, using_lld):
  def is_supported(f):
    if using_lld:
      for flag, takes_arg in UNSUPPORTED_LLD_FLAGS.items():
        # lld allows various flags to have either a single -foo or double --foo
        if f.startswith(flag) or f.startswith('-' + flag):
          diagnostics.warning('linkflags', 'ignoring unsupported linker flag: `%s`', f)
          return False, takes_arg
      return True, False
    else:
      if f in SUPPORTED_LINKER_FLAGS:
        return True, False
      # Silently ignore -l/-L flags when not using lld.  If using lld allow
      # them to pass through the linker
      if f.startswith('-l') or f.startswith('-L'):
        return False, False
      diagnostics.warning('linkflags', 'ignoring unsupported linker flag: `%s`', f)
      return False, False

  results = []
  skip_next = False
  for f in flags:
    if skip_next:
      skip_next = False
      continue
    keep, skip_next = is_supported(f[1])
    if keep:
      results.append(f)

  return results


def fix_windows_newlines(text):
  # Avoid duplicating \r\n to \r\r\n when writing out text.
  if WINDOWS:
    text = text.replace('\r\n', '\n')
  return text


def cxx_to_c_compiler(cxx):
  # Convert C++ compiler name into C compiler name
  dirname, basename = os.path.split(cxx)
  basename = basename.replace('clang++', 'clang').replace('g++', 'gcc').replace('em++', 'emcc')
  return os.path.join(dirname, basename)


def backend_binaryen_passes():
  # wasm backend output can benefit from the binaryen optimizer (in asm2wasm,
  # we run the optimizer during asm2wasm itself). use it, if not overridden.

  # run the binaryen optimizer in -O2+. in -O0 we don't need it obviously, while
  # in -O1 we don't run it as the LLVM optimizer has been run, and it does the
  # great majority of the work; not running the binaryen optimizer in that case
  # keeps -O1 mostly-optimized while compiling quickly and without rewriting
  # DWARF etc.
  run_binaryen_optimizer = shared.Settings.OPT_LEVEL >= 2

  passes = []
  # safe heap must run before post-emscripten, so post-emscripten can apply the sbrk ptr
  if shared.Settings.SAFE_HEAP:
    passes += ['--safe-heap']
  if run_binaryen_optimizer:
    passes += ['--post-emscripten']
    if not shared.Settings.EXIT_RUNTIME:
      passes += ['--no-exit-runtime']
  if run_binaryen_optimizer:
    passes += [building.opt_level_to_str(shared.Settings.OPT_LEVEL, shared.Settings.SHRINK_LEVEL)]
  elif shared.Settings.STANDALONE_WASM:
    # even if not optimizing, make an effort to remove all unused imports and
    # exports, to make the wasm as standalone as possible
    passes += ['--remove-unused-module-elements']
  # when optimizing, use the fact that low memory is never used (1024 is a
  # hardcoded value in the binaryen pass)
  if run_binaryen_optimizer and shared.Settings.GLOBAL_BASE >= 1024:
    passes += ['--low-memory-unused']
  if shared.Settings.AUTODEBUG:
    # adding '--flatten' here may make these even more effective
    passes += ['--instrument-locals']
    passes += ['--log-execution']
    passes += ['--instrument-memory']
    if shared.Settings.LEGALIZE_JS_FFI:
      # legalize it again now, as the instrumentation may need it
      passes += ['--legalize-js-interface']
  if shared.Settings.EMULATE_FUNCTION_POINTER_CASTS:
    # note that this pass must run before asyncify, as if it runs afterwards we only
    # generate the  byn$fpcast_emu  functions after asyncify runs, and so we wouldn't
    # be able to further process them.
    passes += ['--fpcast-emu']
  if shared.Settings.ASYNCIFY:
    passes += ['--asyncify']
    if shared.Settings.ASSERTIONS:
      passes += ['--pass-arg=asyncify-asserts']
    if shared.Settings.ASYNCIFY_ADVISE:
      passes += ['--pass-arg=asyncify-verbose']
    if shared.Settings.ASYNCIFY_IGNORE_INDIRECT:
      passes += ['--pass-arg=asyncify-ignore-indirect']
    else:
      # if we are not ignoring indirect calls, then we must treat invoke_* as if
      # they are indirect calls, since that is what they do - we can't see their
      # targets statically.
      shared.Settings.ASYNCIFY_IMPORTS += ['invoke_*']
    # with pthreads we may call main through the __call_main mechanism, which can
    # therefore reach anything in the program, so mark it as possibly causing a
    # sleep (the asyncify analysis doesn't look through JS, just wasm, so it can't
    # see what it itself calls)
    if shared.Settings.USE_PTHREADS:
      shared.Settings.ASYNCIFY_IMPORTS += ['__call_main']
    # add the default imports
    shared.Settings.ASYNCIFY_IMPORTS += DEFAULT_ASYNCIFY_IMPORTS

    # return the full import name, including module. The name may
    # already have a module prefix; if not, we assume it is "env".
    def get_full_import_name(name):
      if '.' in name:
        return name
      return 'env.' + name

    shared.Settings.ASYNCIFY_IMPORTS = [get_full_import_name(i) for i in shared.Settings.ASYNCIFY_IMPORTS]

    passes += ['--pass-arg=asyncify-imports@%s' % ','.join(shared.Settings.ASYNCIFY_IMPORTS)]

    # shell escaping can be confusing; try to emit useful warnings
    def check_human_readable_list(items):
      for item in items:
        if item.count('(') != item.count(')'):
          logger.warning('''emcc: ASYNCIFY list contains an item without balanced parentheses ("(", ")"):''')
          logger.warning('''   ''' + item)
          logger.warning('''This may indicate improper escaping that led to splitting inside your names.''')
          logger.warning('''Try to quote the entire argument, like this: -s 'ASYNCIFY_ONLY=["foo(int, char)", "bar"]' ''')
          break

    if shared.Settings.ASYNCIFY_REMOVE:
      check_human_readable_list(shared.Settings.ASYNCIFY_REMOVE)
      passes += ['--pass-arg=asyncify-removelist@%s' % ','.join(shared.Settings.ASYNCIFY_REMOVE)]
    if shared.Settings.ASYNCIFY_ADD:
      check_human_readable_list(shared.Settings.ASYNCIFY_ADD)
      passes += ['--pass-arg=asyncify-addlist@%s' % ','.join(shared.Settings.ASYNCIFY_ADD)]
    if shared.Settings.ASYNCIFY_ONLY:
      check_human_readable_list(shared.Settings.ASYNCIFY_ONLY)
      passes += ['--pass-arg=asyncify-onlylist@%s' % ','.join(shared.Settings.ASYNCIFY_ONLY)]
  if shared.Settings.BINARYEN_IGNORE_IMPLICIT_TRAPS:
    passes += ['--ignore-implicit-traps']

  if shared.Settings.BINARYEN_EXTRA_PASSES:
    # BINARYEN_EXTRA_PASSES is comma-separated, and we support both '-'-prefixed and
    # unprefixed pass names
    extras = shared.Settings.BINARYEN_EXTRA_PASSES.split(',')
    passes += [('--' + p) if p[0] != '-' else p for p in extras if p]

  return passes


def make_js_executable(script):
  src = open(script).read()
  cmd = shared.shlex_join(shared.JS_ENGINE)
  if not os.path.isabs(shared.JS_ENGINE[0]):
    # TODO: use whereis etc. And how about non-*NIX?
    cmd = '/usr/bin/env -S ' + cmd
  logger.debug('adding `#!` to JavaScript file: %s' % cmd)
  # add shebang
  with open(script, 'w') as f:
    f.write('#!%s\n' % cmd)
    f.write(src)
  try:
    os.chmod(script, stat.S_IMODE(os.stat(script).st_mode) | stat.S_IXUSR) # make executable
  except OSError:
    pass # can fail if e.g. writing the executable to /dev/null


run_via_emxx = False


#
# Main run() function
#
def run(args):
  global final_js
  target = None

  # Additional compiler flags that we treat as if they were passed to us on the
  # commandline
  EMCC_CFLAGS = os.environ.get('EMCC_CFLAGS')
  if DEBUG:
    cmd = shared.shlex_join(args)
    if EMCC_CFLAGS:
      cmd += ' + ' + EMCC_CFLAGS
    logger.warning('invocation: ' + cmd + '  (in ' + os.getcwd() + ')')
  if EMCC_CFLAGS:
    args.extend(shlex.split(EMCC_CFLAGS))

  # Strip args[0] (program name)
  args = args[1:]

  misc_temp_files = shared.configuration.get_temp_files()

  # Handle some global flags

  # read response files very early on
  try:
    args = substitute_response_files(args)
  except IOError as e:
    exit_with_error(e)

  if '--help' in args:
    # Documentation for emcc and its options must be updated in:
    #    site/source/docs/tools_reference/emcc.rst
    # This then gets built (via: `make -C site text`) to:
    #    site/build/text/docs/tools_reference/emcc.txt
    # This then needs to be copied to its final home in docs/emcc.txt from where
    # we read it here.  We have CI rules that ensure its always up-to-date.
    with open(shared.path_from_root('docs', 'emcc.txt'), 'r') as f:
      print(f.read())

    print('''
------------------------------------------------------------------

emcc: supported targets: llvm bitcode, javascript, NOT elf
(autoconf likes to see elf above to enable shared object support)
''')
    return 0

  if '--version' in args:
    # if the emscripten folder is not a git repo, don't run git show - that can
    # look up and find the revision in a parent directory that is a git repo
    revision = ''
    if os.path.exists(shared.path_from_root('.git')):
      revision = run_process(['git', 'rev-parse', 'HEAD'], stdout=PIPE, stderr=PIPE, cwd=shared.path_from_root()).stdout.strip()
    elif os.path.exists(shared.path_from_root('emscripten-revision.txt')):
      revision = open(shared.path_from_root('emscripten-revision.txt')).read().strip()
    if revision:
      revision = ' (%s)' % revision
    print('''emcc (Emscripten gcc/clang-like replacement) %s%s
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  ''' % (shared.EMSCRIPTEN_VERSION, revision))
    return 0

  CXX = [shared.CLANG_CXX]
  CC = [shared.CLANG_CC]
  if shared.COMPILER_WRAPPER:
    logger.debug('using compiler wrapper: %s', shared.COMPILER_WRAPPER)
    CXX.insert(0, shared.COMPILER_WRAPPER)
    CC.insert(0, shared.COMPILER_WRAPPER)

  if run_via_emxx:
    clang = shared.CLANG_CXX
  else:
    clang = shared.CLANG_CC

  if len(args) == 1 and args[0] == '-v': # -v with no inputs
    # autoconf likes to see 'GNU' in the output to enable shared object support
    print('emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) %s' % shared.EMSCRIPTEN_VERSION, file=sys.stderr)
    code = shared.check_call([clang, '-v'], check=False).returncode
    shared.check_sanity(force=True)
    return code

  shared.check_sanity(force=DEBUG)

  if '-dumpmachine' in args:
    print(shared.get_llvm_target())
    return 0

  if '-dumpversion' in args: # gcc's doc states "Print the compiler version [...] and don't do anything else."
    print(shared.EMSCRIPTEN_VERSION)
    return 0

  if '--cflags' in args:
    # fake running the command, to see the full args we pass to clang
    args = [x for x in args if x != '--cflags']
    with misc_temp_files.get_file(suffix='.o') as temp_target:
      input_file = 'hello_world.c'
      cmd = [shared.PYTHON, sys.argv[0], shared.path_from_root('tests', input_file), '-v', '-c', '-o', temp_target] + args
      proc = run_process(cmd, stderr=PIPE, check=False)
      if proc.returncode != 0:
        print(proc.stderr)
        exit_with_error('error getting cflags')
      lines = [x for x in proc.stderr.splitlines() if clang in x and input_file in x]
      parts = shlex.split(lines[0].replace('\\', '\\\\'))
      parts = [x for x in parts if x not in ['-c', '-o', '-v', '-emit-llvm'] and input_file not in x and temp_target not in x]
      print(shared.shlex_join(parts[1:]))
    return 0

  def get_language_mode(args):
    return_next = False
    for item in args:
      if return_next:
        return item
      if item == '-x':
        return_next = True
        continue
      if item.startswith('-x'):
        return item[2:]
    return ''

  language_mode = get_language_mode(args)

  def is_dash_s_for_emcc(args, i):
    # -s OPT=VALUE or -s OPT or -sOPT are all interpreted as emscripten flags.
    # -s by itself is a linker option (alias for --strip-all)
    if args[i] == '-s':
      if len(args) <= i + 1:
        return False
      arg = args[i + 1]
    else:
      arg = args[i][2:]
    return arg.split('=')[0].isupper()

  EMMAKEN_CFLAGS = os.environ.get('EMMAKEN_CFLAGS')
  if EMMAKEN_CFLAGS:
    args += shlex.split(EMMAKEN_CFLAGS)

  # ---------------- Utilities ---------------

  seen_names = {}

  def uniquename(name):
    if name not in seen_names:
      seen_names[name] = str(len(seen_names))
    return unsuffixed(name) + '_' + seen_names[name] + shared.suffix(name)

  # ---------------- End configs -------------

  temp_dir = shared.get_emscripten_temp_dir()

  def in_temp(name):
    return os.path.join(temp_dir, os.path.basename(name))

  def get_file_suffix(filename):
    """Parses the essential suffix of a filename, discarding Unix-style version
    numbers in the name. For example for 'libz.so.1.2.8' returns '.so'"""
    if filename in SPECIAL_ENDINGLESS_FILENAMES:
      return filename
    while filename:
      filename, suffix = os.path.splitext(filename)
      if not suffix[1:].isdigit():
        return suffix
    return ''

  def optimizing(opts):
    return '-O0' not in opts

  def need_llvm_debug_info():
    return shared.Settings.DEBUG_LEVEL >= 3

  with ToolchainProfiler.profile_block('parse arguments and setup'):
    ## Parse args

    newargs = list(args)

    # Scan and strip emscripten specific cmdline warning flags.
    # This needs to run before other cmdline flags have been parsed, so that
    # warnings are properly printed during arg parse.
    newargs = diagnostics.capture_warnings(newargs)

    if not shared.CONFIG_FILE:
      diagnostics.warning('deprecated', 'Specifying EM_CONFIG as a python literal is deprecated. Please use a file instead.')

    if sys.version_info < (3, 0, 0) and 'EMCC_ALLOW_PYTHON2' not in os.environ:
      diagnostics.warning('deprecated', 'Support for running emscripten with python2 is deprecated.  Please update to python3 as soon as possible (See https://github.com/emscripten-core/emscripten/issues/7198')

    for i in range(len(newargs)):
      if newargs[i] in ('-l', '-L', '-I'):
        # Scan for individual -l/-L/-I arguments and concatenate the next arg on
        # if there is no suffix
        newargs[i] += newargs[i + 1]
        newargs[i + 1] = ''

    options, settings_changes, user_js_defines, newargs = parse_args(newargs)

    if 'EMMAKEN_COMPILER' in os.environ:
      diagnostics.warning('deprecated', '`EMMAKEN_COMPILER` is deprecated.\n'
                          'To use an alteranative LLVM build set `LLVM_ROOT` in the config file (or `EM_LLVM_ROOT` env var).\n'
                          'To wrap invocations of clang use the `COMPILER_WRAPPER` setting (or `EM_COMPILER_WRAPPER` env var.\n')
      CXX = [os.environ['EMMAKEN_COMPILER']]
      CC = [cxx_to_c_compiler(os.environ['EMMAKEN_COMPILER'])]

    if '-print-search-dirs' in newargs:
      return run_process(CC + ['-print-search-dirs'], check=False).returncode

    if options.emrun:
      options.pre_js += open(shared.path_from_root('src', 'emrun_prejs.js')).read() + '\n'
      options.post_js += open(shared.path_from_root('src', 'emrun_postjs.js')).read() + '\n'
      # emrun mode waits on program exit
      shared.Settings.EXIT_RUNTIME = 1

    if options.cpu_profiler:
      options.post_js += open(shared.path_from_root('src', 'cpuprofiler.js')).read() + '\n'

    if options.memory_profiler:
      shared.Settings.MEMORYPROFILER = 1

    if options.thread_profiler:
      options.post_js += open(shared.path_from_root('src', 'threadprofiler.js')).read() + '\n'

    if options.llvm_opts is None:
      options.llvm_opts = LLVM_OPT_LEVEL[shared.Settings.OPT_LEVEL]
    elif type(options.llvm_opts) == int:
      options.llvm_opts = ['-O%d' % options.llvm_opts]

    if options.memory_init_file is None:
      options.memory_init_file = shared.Settings.OPT_LEVEL >= 2

    # TODO: support source maps with js_transform
    if options.js_transform and use_source_map():
      logger.warning('disabling source maps because a js transform is being done')
      shared.Settings.DEBUG_LEVEL = 3

    if DEBUG:
      start_time = time.time() # done after parsing arguments, which might affect debug state

    for i in range(len(newargs)):
      if newargs[i].startswith('-s'):
        if is_dash_s_for_emcc(newargs, i):
          if newargs[i] == '-s':
            key = newargs[i + 1]
            newargs[i + 1] = ''
          else:
            key = newargs[i][2:]
          newargs[i] = ''

          # If not = is specified default to 1
          if '=' not in key:
            key += '=1'

          # Special handling of browser version targets. A version -1 means that the specific version
          # is not supported at all. Replace those with INT32_MAX to make it possible to compare e.g.
          # #if MIN_FIREFOX_VERSION < 68
          try:
            if re.match(r'MIN_.*_VERSION(=.*)?', key) and int(key.split('=')[1]) < 0:
              key = key.split('=')[0] + '=0x7FFFFFFF'
          except Exception:
            pass

          settings_changes.append(key)

    newargs = [arg for arg in newargs if arg]

    settings_key_changes = {}
    for s in settings_changes:
      key, value = s.split('=', 1)
      settings_key_changes[key] = value

    # Find input files

    # These three arrays are used to store arguments of different types for
    # type-specific processing. In order to shuffle the arguments back together
    # after processing, all of these arrays hold tuples (original_index, value).
    # Note that the index part of the tuple can have a fractional part for input
    # arguments that expand into multiple processed arguments, as in -Wl,-f1,-f2.
    input_files = []
    libs = []
    link_flags = []

    # All of the above arg lists entries contain indexes into the full argument
    # list. In order to add extra implicit args (embind.cc, etc) below, we keep a
    # counter for the next index that should be used.
    next_arg_index = len(newargs)

    has_header_inputs = False
    lib_dirs = []

    has_dash_c = '-c' in newargs
    has_dash_S = '-S' in newargs
    has_dash_E = '-E' in newargs

    compile_only = has_dash_c or has_dash_S or has_dash_E

    def add_link_flag(i, f):
      # Filter out libraries that musl includes in libc itself, or which we
      # otherwise provide implicitly.
      if f in ('-lm', '-lrt', '-ldl', '-lpthread'):
        return
      if f.startswith('-l'):
        libs.append((i, f[2:]))
      if f.startswith('-L'):
        lib_dirs.append(f[2:])

      link_flags.append((i, f))

    # find input files with a simple heuristic. we should really analyze
    # based on a full understanding of gcc params, right now we just assume that
    # what is left contains no more |-x OPT| things
    skip = False
    for i in range(len(newargs)):
      if skip:
        skip = False
        continue

      arg = newargs[i]
      if arg in ('-MT', '-MF', '-MJ', '-MQ', '-D', '-U', '-o', '-x',
                 '-Xpreprocessor', '-include', '-imacros', '-idirafter',
                 '-iprefix', '-iwithprefix', '-iwithprefixbefore',
                 '-isysroot', '-imultilib', '-A', '-isystem', '-iquote',
                 '-install_name', '-compatibility_version',
                 '-current_version', '-I', '-L', '-include-pch',
                 '-Xlinker', '-Xclang'):
        skip = True

      if not arg.startswith('-'):
        # os.devnul should always be reported as existing but there is bug in windows
        # python before 3.8:
        # https://bugs.python.org/issue1311
        if not os.path.exists(arg) and arg != os.devnull:
          exit_with_error('%s: No such file or directory ("%s" was expected to be an input file, based on the commandline arguments provided)', arg, arg)
        file_suffix = get_file_suffix(arg)
        if file_suffix in SOURCE_ENDINGS + DYNAMICLIB_ENDINGS + ASSEMBLY_ENDINGS + HEADER_ENDINGS or building.is_ar(arg):
          # we already removed -o <target>, so all these should be inputs
          newargs[i] = ''
          if file_suffix in SOURCE_ENDINGS or (has_dash_c and file_suffix == '.bc'):
            input_files.append((i, arg))
          elif file_suffix in HEADER_ENDINGS:
            input_files.append((i, arg))
            has_header_inputs = True
          elif file_suffix in ASSEMBLY_ENDINGS or building.is_bitcode(arg) or building.is_ar(arg):
            input_files.append((i, arg))
          elif building.is_wasm(arg):
            input_files.append((i, arg))
          elif file_suffix in (STATICLIB_ENDINGS + DYNAMICLIB_ENDINGS):
            # if it's not, and it's a library, just add it to libs to find later
            libname = unsuffixed_basename(arg)
            for prefix in LIB_PREFIXES:
              if not prefix:
                continue
              if libname.startswith(prefix):
                libname = libname[len(prefix):]
                break
            libs.append((i, libname))
        elif file_suffix in STATICLIB_ENDINGS:
          if not building.is_ar(arg):
            if building.is_bitcode(arg):
              message = arg + ': File has a suffix of a static library ' + str(STATICLIB_ENDINGS) + ', but instead is an LLVM bitcode file! When linking LLVM bitcode files use .bc or .o.'
            else:
              message = arg + ': Unknown format, not a static library!'
            exit_with_error(message)
        else:
          newargs[i] = ''
          input_files.append((i, arg))
      elif arg.startswith('-L'):
        add_link_flag(i, arg)
        newargs[i] = ''
      elif arg.startswith('-l'):
        add_link_flag(i, arg)
        newargs[i] = ''
      elif arg.startswith('-Wl,'):
        # Multiple comma separated link flags can be specified. Create fake
        # fractional indices for these: -Wl,a,b,c,d at index 4 becomes:
        # (4, a), (4.25, b), (4.5, c), (4.75, d)
        link_flags_to_add = arg.split(',')[1:]
        for flag_index, flag in enumerate(link_flags_to_add):
          add_link_flag(i + float(flag_index) / len(link_flags_to_add), flag)
        newargs[i] = ''
      elif arg == '-Xlinker':
        add_link_flag(i + 1, newargs[i + 1])
        newargs[i] = ''
        newargs[i + 1] = ''
      elif arg == '-s':
        # -s and some other compiler flags are normally passed onto the linker
        # TODO(sbc): Pass this and other flags through when using lld
        # link_flags.append((i, arg))
        newargs[i] = ''
      elif arg == '-':
        input_files.append((i, arg))
        newargs[i] = ''
    newargs = [a for a in newargs if a]

    # Libraries are searched before settings_changes are applied, so apply the
    # value for STRICT from command line already now.

    strict_cmdline = settings_key_changes.get('STRICT')
    if strict_cmdline:
      shared.Settings.STRICT = int(strict_cmdline)

    # Apply optimization level settings
    shared.Settings.apply_opt_level(opt_level=shared.Settings.OPT_LEVEL, shrink_level=shared.Settings.SHRINK_LEVEL, noisy=True)

    # For users that opt out of WARN_ON_UNDEFINED_SYMBOLS we assume they also
    # want to opt out of ERROR_ON_UNDEFINED_SYMBOLS.
    if 'WARN_ON_UNDEFINED_SYMBOLS=0' in settings_changes:
      shared.Settings.ERROR_ON_UNDEFINED_SYMBOLS = 0

    if shared.Settings.MINIMAL_RUNTIME or 'MINIMAL_RUNTIME=1' in settings_changes or 'MINIMAL_RUNTIME=2' in settings_changes:
      # Remove the default exported functions 'malloc', 'free', etc. those should only be linked in if used
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE = []

    # Apply -s settings in newargs here (after optimization levels, so they can override them)
    apply_settings(settings_changes)

    # Check if a target is specified on the command line
    specified_target, args = find_output_arg(args)

    make_output_executable = False

    if os.environ.get('EMMAKEN_JUST_CONFIGURE') or 'conftest.c' in args:
      # configure tests want a more shell-like style, where we emit return codes on exit()
      shared.Settings.EXIT_RUNTIME = 1
      # use node.js raw filesystem access, to behave just like a native executable
      shared.Settings.NODERAWFS = 1
      # Add `#!` line to output JS and make it executable.
      make_output_executable = True
      # Autoconf expects the executable output file to be called `a.out`
      default_target_name = 'a.out'
    elif shared.Settings.SIDE_MODULE:
      default_target_name = 'a.out.wasm'
    else:
      default_target_name = 'a.out.js'

    # specified_target is the user-specified one, target is what we will generate
    if specified_target:
      target = specified_target
      # check for the existence of the output directory now, to avoid having
      # to do so repeatedly when each of the various output files (.mem, .wasm,
      # etc) are written. This gives a more useful error message than the
      # IOError and python backtrace that users would otherwise see.
      dirname = os.path.dirname(target)
      if dirname and not os.path.isdir(dirname):
        exit_with_error("specified output file (%s) is in a directory that does not exist" % target)
    else:
      target = default_target_name

    shared.Settings.TARGET_BASENAME = target_basename = unsuffixed_basename(target)

    final_suffix = get_file_suffix(target)

    if has_dash_c or has_dash_S or has_dash_E:
      if has_dash_c:
        if '-emit-llvm' in newargs:
          final_suffix = '.bc'
        else:
          final_suffix = options.default_object_extension
        target = target_basename + final_suffix
      elif has_dash_S:
        if '-emit-llvm' in newargs:
          final_suffix = '.ll'
        else:
          final_suffix = '.s'
        target = target_basename + final_suffix

      if len(input_files) > 1 and specified_target:
        exit_with_error('cannot specify -o with -c/-S/-E and multiple source files')

    if '-M' in newargs or '-MM' in newargs:
      final_suffix = '.mout' # not bitcode, not js; but just dependency rule of the input file

    # target is now finalized, can finalize other _target s
    if final_suffix == '.mjs':
      shared.Settings.EXPORT_ES6 = 1
      shared.Settings.MODULARIZE = 1

    if shared.Settings.SIDE_MODULE or final_suffix in WASM_ENDINGS:
      # If the user asks directly for a wasm file then this *is* the target
      wasm_target = target
    else:
      # Otherwise the wasm file is produced alongside the final target.
      wasm_target = unsuffixed(target) + '.wasm'

    wasm_source_map_target = wasm_target + '.map'

    # Apply user -jsD settings
    for s in user_js_defines:
      shared.Settings.attrs[s[0]] = s[1]

    shared.verify_settings()

    if final_suffix in WASM_ENDINGS and not shared.Settings.SIDE_MODULE:
      # if the output is just a wasm file, it will normally be a standalone one,
      # as there is no JS. an exception are side modules, as we can't tell at
      # compile time whether JS will be involved or not - the main module may
      # have JS, and the side module is expected to link against that.
      # we also do not support standalone mode in fastcomp.
      shared.Settings.STANDALONE_WASM = 1

    if shared.Settings.WASM2C:
      # wasm2c only makes sense with standalone wasm - there will be no JS,
      # just wasm and then C
      shared.Settings.STANDALONE_WASM = 1
      # wasm2c doesn't need any special handling of i64, we have proper i64
      # handling on the FFI boundary, which is exactly like the case of JS with
      # BigInt support
      shared.Settings.WASM_BIGINT = 1

    if options.no_entry:
      shared.Settings.EXPECT_MAIN = 0
    elif shared.Settings.STANDALONE_WASM:
      if '_main' in shared.Settings.EXPORTED_FUNCTIONS:
        # TODO(sbc): Make this into a warning?
        logger.debug('including `_main` in EXPORTED_FUNCTIONS is not necessary in standalone mode')
    else:
      # In normal non-standalone mode we have special handling of `_main` in EXPORTED_FUNCTIONS.
      # 1. If the user specifies exports, but doesn't include `_main` we assume they want to build a
      #    reactor.
      # 2. If the user doesn't export anything we default to exporting `_main` (unless `--no-entry`
      #    is specified (see above).
      if 'EXPORTED_FUNCTIONS' in settings_key_changes:
        if '_main' not in shared.Settings.USER_EXPORTED_FUNCTIONS:
          shared.Settings.EXPECT_MAIN = 0
      else:
        assert(not shared.Settings.EXPORTED_FUNCTIONS)
        shared.Settings.EXPORTED_FUNCTIONS = ['_main']

    if shared.Settings.STANDALONE_WASM:
      # In STANDALONE_WASM mode we either build a command or a reactor.
      # See https://github.com/WebAssembly/WASI/blob/master/design/application-abi.md
      # For a command we always want EXIT_RUNTIME=1
      # For a reactor we always want EXIT_RUNTIME=0
      if 'EXIT_RUNTIME' in settings_key_changes:
        exit_with_error('Explictly setting EXIT_RUNTIME not compatible with STANDALONE_WASM.  EXIT_RUNTIME will always be True for programs (with a main function) and False for reactors (not main function).')
      shared.Settings.EXIT_RUNTIME = shared.Settings.EXPECT_MAIN

    def filter_out_dynamic_libs(inputs):
      # If not compiling to JS, then we are compiling to an intermediate bitcode
      # objects or library, so ignore dynamic linking, since multiple dynamic
      # linkings can interfere with each other
      if final_suffix not in EXECUTABLE_ENDINGS or options.ignore_dynamic_linking:
        def check(input_file):
          if get_file_suffix(input_file) in DYNAMICLIB_ENDINGS:
            if not options.ignore_dynamic_linking:
              diagnostics.warning('emcc', 'ignoring dynamic library %s because not compiling to JS or HTML, remember to link it when compiling to JS or HTML at the end', os.path.basename(input_file))
            return False
          else:
            return True
        return [f for f in inputs if check(f[1])]
      return inputs

    def filter_out_duplicate_dynamic_libs(inputs):
      # Filter out duplicate shared libraries.
      # See test_core.py:test_redundant_link
      seen = set()
      rtn = []
      for i in inputs:
        if get_file_suffix(i[1]) in DYNAMICLIB_ENDINGS and os.path.exists(i[1]):
          abspath = os.path.abspath(i[1])
          if abspath in seen:
            continue
          seen.add(abspath)
        rtn.append(i)
      return rtn

    input_files = filter_out_dynamic_libs(input_files)
    input_files = filter_out_duplicate_dynamic_libs(input_files)

    if not input_files and not link_flags:
      exit_with_error('no input files')

    # Note the exports the user requested
    building.user_requested_exports = shared.Settings.EXPORTED_FUNCTIONS[:]

    # -s ASSERTIONS=1 implies basic stack overflow checks.
    if shared.Settings.ASSERTIONS:
      shared.Settings.STACK_OVERFLOW_CHECK = max(1, shared.Settings.STACK_OVERFLOW_CHECK)

    if shared.Settings.LLD_REPORT_UNDEFINED or shared.Settings.STANDALONE_WASM:
      # Reporting undefined symbols at wasm-ld time requires us to know if we have a `main` function
      # or not, as does standalone wasm mode.
      # TODO(sbc): Remove this once this becomes the default
      shared.Settings.IGNORE_MISSING_MAIN = 0

    if shared.Settings.STRICT:
      shared.Settings.STRICT_JS = 1
      shared.Settings.AUTO_JS_LIBRARIES = 0
      shared.Settings.AUTO_ARCHIVE_INDEXES = 0
      shared.Settings.IGNORE_MISSING_MAIN = 0
      shared.Settings.DEFAULT_TO_CXX = 0

    # If set to 1, we will run the autodebugger (the automatic debugging tool, see
    # tools/autodebugger).  Note that this will disable inclusion of libraries. This
    # is useful because including dlmalloc makes it hard to compare native and js
    # builds
    if os.environ.get('EMCC_AUTODEBUG'):
      shared.Settings.AUTODEBUG = 1

    # Use settings

    if shared.Settings.DEBUG_LEVEL > 1 and options.use_closure_compiler:
      diagnostics.warning('emcc', 'disabling closure because debug info was requested')
      options.use_closure_compiler = False

    if shared.Settings.WASM == 2 and shared.Settings.SINGLE_FILE:
      exit_with_error('cannot have both WASM=2 and SINGLE_FILE enabled at the same time')

    if shared.Settings.SEPARATE_DWARF and shared.Settings.WASM2JS:
      exit_with_error('cannot have both SEPARATE_DWARF and WASM2JS at the same time (as there is no wasm file)')

    if shared.Settings.MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and shared.Settings.MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION:
      exit_with_error('MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION and MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION are mutually exclusive!')

    if options.emrun:
      if shared.Settings.MINIMAL_RUNTIME:
        exit_with_error('--emrun is not compatible with -s MINIMAL_RUNTIME=1')
      shared.Settings.EXPORTED_RUNTIME_METHODS.append('addOnExit')

    if options.use_closure_compiler:
      shared.Settings.USE_CLOSURE_COMPILER = options.use_closure_compiler

    if shared.Settings.CLOSURE_WARNINGS not in ['quiet', 'warn', 'error']:
      exit_with_error('Invalid option -s CLOSURE_WARNINGS=%s specified! Allowed values are "quiet", "warn" or "error".' % shared.Settings.CLOSURE_WARNINGS)

    if shared.Settings.MAIN_MODULE:
      assert not shared.Settings.SIDE_MODULE
      if shared.Settings.MAIN_MODULE == 1:
        shared.Settings.INCLUDE_FULL_LIBRARY = 1
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$preloadDylibs']
    elif shared.Settings.SIDE_MODULE:
      assert not shared.Settings.MAIN_MODULE
      # memory init file is not supported with asm.js side modules, must be executable synchronously (for dlopen)
      options.memory_init_file = False

    if shared.Settings.MAIN_MODULE or shared.Settings.SIDE_MODULE:
      if shared.Settings.MAIN_MODULE == 1 or shared.Settings.SIDE_MODULE == 1:
        shared.Settings.LINKABLE = 1
        shared.Settings.EXPORT_ALL = 1
      shared.Settings.RELOCATABLE = 1

    if shared.Settings.RELOCATABLE:
      if options.use_closure_compiler:
        exit_with_error('cannot use closure compiler on shared modules')
      if shared.Settings.MINIMAL_RUNTIME:
        exit_with_error('MINIMAL_RUNTIME is not compatible with relocatable output')
      # shared modules need memory utilities to allocate their memory
      shared.Settings.EXPORTED_RUNTIME_METHODS += ['allocate']
      shared.Settings.ALLOW_TABLE_GROWTH = 1
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$relocateExports']

    # various settings require sbrk() access
    if shared.Settings.DETERMINISTIC or \
       shared.Settings.EMSCRIPTEN_TRACING or \
       shared.Settings.MALLOC == 'emmalloc' or \
       shared.Settings.SAFE_HEAP or \
       shared.Settings.MEMORYPROFILER:
      shared.Settings.EXPORTED_FUNCTIONS += ['_sbrk']

    if shared.Settings.MEMORYPROFILER:
      shared.Settings.EXPORTED_FUNCTIONS += ['___heap_base']

    if shared.Settings.ASYNCIFY:
      # See: https://github.com/emscripten-core/emscripten/issues/12065
      # See: https://github.com/emscripten-core/emscripten/issues/12066
      shared.Settings.USE_LEGACY_DYNCALLS = 1
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$getDynCaller']

    # Reconfigure the cache now that settings have been applied. Some settings
    # such as LTO and SIDE_MODULE/MAIN_MODULE effect which cache directory we use.
    shared.reconfigure_cache()

    if not compile_only:
      ldflags = shared.emsdk_ldflags(newargs)
      for f in ldflags:
        newargs.append(f)
        add_link_flag(len(newargs), f)

    # Flags we pass to the compiler when building C/C++ code
    # We add these to the user's flags (newargs), but not when building .s or .S assembly files
    cflags = []

    # SSEx is implemented on top of SIMD128 instruction set, but do not pass SSE flags to LLVM
    # so it won't think about generating native x86 SSE code.
    newargs = [x for x in newargs if x not in shared.SIMD_INTEL_FEATURE_TOWER and x not in shared.SIMD_NEON_FLAGS]

    if not shared.Settings.STRICT:
      # The preprocessor define EMSCRIPTEN is deprecated. Don't pass it to code
      # in strict mode. Code should use the define __EMSCRIPTEN__ instead.
      cflags.append('-DEMSCRIPTEN')

    link_to_object = False
    if options.shared or options.relocatable:
      # Until we have a better story for actually producing runtime shared libraries
      # we support a compatibility mode where shared libraries are actually just
      # object files linked with `wasm-ld --relocatable` or `llvm-link` in the case
      # of LTO.
      if final_suffix in EXECUTABLE_ENDINGS:
        diagnostics.warning('emcc', '-shared/-r used with executable output suffix. This behaviour is deprecated.  Please remove -shared/-r to build an executable or avoid the executable suffix (%s) when building object files.' % final_suffix)
      else:
        if options.shared:
          diagnostics.warning('emcc', 'linking a library with `-shared` will emit a static object file.  This is a form of emulation to support existing build systems.  If you want to build a runtime shared library use the SIDE_MODULE setting.')
        link_to_object = True

    if shared.Settings.STACK_OVERFLOW_CHECK:
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$abortStackOverflow']
      shared.Settings.EXPORTED_RUNTIME_METHODS += ['writeStackCookie', 'checkStackCookie']

    if shared.Settings.MODULARIZE:
      assert not options.proxy_to_worker, '-s MODULARIZE=1 is not compatible with --proxy-to-worker (if you want to run in a worker with -s MODULARIZE=1, you likely want to do the worker side setup manually)'
      # in MINIMAL_RUNTIME we may not need to emit the Promise code, as the
      # HTML output creates a singleton instance, and it does so without the
      # Promise. However, in Pthreads mode the Promise is used for worker
      # creation.
      if shared.Settings.MINIMAL_RUNTIME and final_suffix == '.html' and \
         not shared.Settings.USE_PTHREADS:
        shared.Settings.EXPORT_READY_PROMISE = 0

    if shared.Settings.LEGACY_VM_SUPPORT:
      if shared.Settings.WASM2JS:
        shared.Settings.POLYFILL_OLD_MATH_FUNCTIONS = 1

      # Support all old browser versions
      shared.Settings.MIN_FIREFOX_VERSION = 0
      shared.Settings.MIN_SAFARI_VERSION = 0
      shared.Settings.MIN_IE_VERSION = 0
      shared.Settings.MIN_EDGE_VERSION = 0
      shared.Settings.MIN_CHROME_VERSION = 0

    if shared.Settings.MIN_SAFARI_VERSION <= 9 and shared.Settings.WASM2JS:
      shared.Settings.WORKAROUND_IOS_9_RIGHT_SHIFT_BUG = 1

    if shared.Settings.MIN_CHROME_VERSION <= 37:
      shared.Settings.WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG = 1

    setup_environment_settings()

    # Silently drop any individual backwards compatibility emulation flags that are known never to occur on browsers that support WebAssembly.
    if not shared.Settings.WASM2JS:
      shared.Settings.POLYFILL_OLD_MATH_FUNCTIONS = 0
      shared.Settings.WORKAROUND_IOS_9_RIGHT_SHIFT_BUG = 0
      shared.Settings.WORKAROUND_OLD_WEBGL_UNIFORM_UPLOAD_IGNORED_OFFSET_BUG = 0

    if shared.Settings.STB_IMAGE and final_suffix in EXECUTABLE_ENDINGS:
      input_files.append((next_arg_index, shared.path_from_root('third_party', 'stb_image.c')))
      next_arg_index += 1
      shared.Settings.EXPORTED_FUNCTIONS += ['_stbi_load', '_stbi_load_from_memory', '_stbi_image_free']
      # stb_image 2.x need to have STB_IMAGE_IMPLEMENTATION defined to include the implementation when compiling
      cflags.append('-DSTB_IMAGE_IMPLEMENTATION')

    if shared.Settings.USE_WEBGL2:
      shared.Settings.MAX_WEBGL_VERSION = 2

    if not shared.Settings.GL_SUPPORT_SIMPLE_ENABLE_EXTENSIONS and shared.Settings.GL_SUPPORT_AUTOMATIC_ENABLE_EXTENSIONS:
      exit_with_error('-s GL_SUPPORT_SIMPLE_ENABLE_EXTENSIONS=0 only makes sense with -s GL_SUPPORT_AUTOMATIC_ENABLE_EXTENSIONS=0!')

    forced_stdlibs = []

    if shared.Settings.ASMFS and final_suffix in EXECUTABLE_ENDINGS:
      forced_stdlibs.append('libasmfs')
      cflags.append('-D__EMSCRIPTEN_ASMFS__=1')
      next_arg_index += 1
      shared.Settings.FILESYSTEM = 0
      shared.Settings.SYSCALLS_REQUIRE_FILESYSTEM = 0
      shared.Settings.FETCH = 1
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_asmfs.js')))

    # Explicitly drop linking in a malloc implementation if program is not using any dynamic allocation calls.
    if not shared.Settings.USES_DYNAMIC_ALLOC:
      shared.Settings.MALLOC = 'none'

    if shared.Settings.MALLOC == 'emmalloc':
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_emmalloc.js')))

    if shared.Settings.FETCH and final_suffix in EXECUTABLE_ENDINGS:
      forced_stdlibs.append('libfetch')
      next_arg_index += 1
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_fetch.js')))
      if shared.Settings.USE_PTHREADS:
        shared.Settings.FETCH_WORKER_FILE = unsuffixed(os.path.basename(target)) + '.fetch.js'

    if shared.Settings.DEMANGLE_SUPPORT:
      shared.Settings.EXPORTED_FUNCTIONS += ['___cxa_demangle']

    if shared.Settings.FULL_ES3:
      shared.Settings.FULL_ES2 = 1
      shared.Settings.MAX_WEBGL_VERSION = max(2, shared.Settings.MAX_WEBGL_VERSION)

    if shared.Settings.EMBIND:
      forced_stdlibs.append('libembind')

    shared.Settings.EXPORTED_FUNCTIONS += ['_stackSave', '_stackRestore', '_stackAlloc']
    # We need to preserve the __data_end symbol so that wasm-emscripten-finalize can determine
    # where static data ends (and correspondingly where the stack begins).
    shared.Settings.EXPORTED_FUNCTIONS += ['___data_end']
    if not shared.Settings.STANDALONE_WASM:
      # in standalone mode, crt1 will call the constructors from inside the wasm
      shared.Settings.EXPORTED_FUNCTIONS.append('___wasm_call_ctors')

    if shared.Settings.RELOCATABLE and not shared.Settings.DYNAMIC_EXECUTION:
      exit_with_error('cannot have both DYNAMIC_EXECUTION=0 and RELOCATABLE enabled at the same time, since RELOCATABLE needs to eval()')

    if shared.Settings.SIDE_MODULE and shared.Settings.GLOBAL_BASE != -1:
      exit_with_error('Cannot set GLOBAL_BASE when building SIDE_MODULE')

    if shared.Settings.RELOCATABLE:
      shared.Settings.ERROR_ON_UNDEFINED_SYMBOLS = 0
      shared.Settings.WARN_ON_UNDEFINED_SYMBOLS = 0

    if shared.Settings.DISABLE_EXCEPTION_THROWING and not shared.Settings.DISABLE_EXCEPTION_CATCHING:
      exit_with_error("DISABLE_EXCEPTION_THROWING was set (probably from -fno-exceptions) but is not compatible with enabling exception catching (DISABLE_EXCEPTION_CATCHING=0). If you don't want exceptions, set DISABLE_EXCEPTION_CATCHING to 1; if you do want exceptions, don't link with -fno-exceptions")

    # if exception catching is disabled, we can prevent that code from being
    # generated in the frontend
    if shared.Settings.DISABLE_EXCEPTION_CATCHING == 1 and not shared.Settings.EXCEPTION_HANDLING:
      cflags.append('-fignore-exceptions')

    if options.proxy_to_worker:
      shared.Settings.PROXY_TO_WORKER = 1

    if options.use_preload_plugins or len(options.preload_files) or len(options.embed_files):
      if shared.Settings.NODERAWFS:
        exit_with_error('--preload-file and --embed-file cannot be used with NODERAWFS which disables virtual filesystem')
      # if we include any files, or intend to use preload plugins, then we definitely need filesystem support
      shared.Settings.FORCE_FILESYSTEM = 1

    if options.proxy_to_worker or options.use_preload_plugins:
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$Browser']

    if not shared.Settings.MINIMAL_RUNTIME:
      # In non-MINIMAL_RUNTIME, the core runtime depends on these functions to be present. (In MINIMAL_RUNTIME, they are
      # no longer always bundled in)
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$demangle', '$demangleAll', '$jsStackTrace', '$stackTrace']

    if shared.Settings.FILESYSTEM:
      # to flush streams on FS exit, we need to be able to call fflush
      # we only include it if the runtime is exitable, or when ASSERTIONS
      # (ASSERTIONS will check that streams do not need to be flushed,
      # helping people see when they should have enabled EXIT_RUNTIME)
      if shared.Settings.EXIT_RUNTIME or shared.Settings.ASSERTIONS:
        shared.Settings.EXPORTED_FUNCTIONS += ['_fflush']

    if shared.Settings.SUPPORT_ERRNO:
      # so setErrNo JS library function can report errno back to C
      shared.Settings.EXPORTED_FUNCTIONS += ['___errno_location']

    if shared.Settings.SAFE_HEAP:
      # SAFE_HEAP check includes calling emscripten_get_sbrk_ptr() from wasm
      shared.Settings.EXPORTED_FUNCTIONS += ['_emscripten_get_sbrk_ptr']
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$unSign']

    if not shared.Settings.DECLARE_ASM_MODULE_EXPORTS:
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$exportAsmFunctions']

    if shared.Settings.ALLOW_MEMORY_GROWTH and 'ABORTING_MALLOC=1' not in settings_changes:
      # Setting ALLOW_MEMORY_GROWTH turns off ABORTING_MALLOC, as in that mode we default to
      # the behavior of trying to grow and returning 0 from malloc on failure, like
      # a standard system would. However, if the user sets the flag it
      # overrides that.
      shared.Settings.ABORTING_MALLOC = 0

    if shared.Settings.USE_PTHREADS:
      if shared.Settings.USE_PTHREADS == 2:
        exit_with_error('USE_PTHREADS=2 is not longer supported')
      if shared.Settings.ALLOW_MEMORY_GROWTH:
        diagnostics.warning('pthreads-mem-growth', 'USE_PTHREADS + ALLOW_MEMORY_GROWTH may run non-wasm code slowly, see https://github.com/WebAssembly/design/issues/1271')
      # UTF8Decoder.decode doesn't work with a view of a SharedArrayBuffer
      shared.Settings.TEXTDECODER = 0
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_pthread.js')))
      cflags.append('-D__EMSCRIPTEN_PTHREADS__=1')
      newargs += ['-pthread']
      # some pthreads code is in asm.js library functions, which are auto-exported; for the wasm backend, we must
      # manually export them

      shared.Settings.EXPORTED_FUNCTIONS += [
        '_emscripten_get_global_libc', '___pthread_tsd_run_dtors',
        'registerPthreadPtr', '_pthread_self',
        '___emscripten_pthread_data_constructor', '_emscripten_futex_wake']

      # set location of worker.js
      shared.Settings.PTHREAD_WORKER_FILE = unsuffixed(os.path.basename(target)) + '.worker.js'
    else:
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_pthread_stub.js')))

    if shared.Settings.FORCE_FILESYSTEM and not shared.Settings.MINIMAL_RUNTIME:
      # when the filesystem is forced, we export by default methods that filesystem usage
      # may need, including filesystem usage from standalone file packager output (i.e.
      # file packages not built together with emcc, but that are loaded at runtime
      # separately, and they need emcc's output to contain the support they need)
      if not shared.Settings.ASMFS:
        shared.Settings.EXPORTED_RUNTIME_METHODS += [
          'FS_createPath',
          'FS_createDataFile',
          'FS_createPreloadedFile',
          'FS_createLazyFile',
          'FS_createDevice',
          'FS_unlink'
        ]

      shared.Settings.EXPORTED_RUNTIME_METHODS += [
        'addRunDependency',
        'removeRunDependency',
      ]

    if not shared.Settings.MINIMAL_RUNTIME or shared.Settings.EXIT_RUNTIME:
      # MINIMAL_RUNTIME only needs callRuntimeCallbacks in certain cases, but the normal runtime
      # always does.
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$callRuntimeCallbacks', '$dynCall']

    if shared.Settings.USE_PTHREADS:
      # memalign is used to ensure allocated thread stacks are aligned.
      shared.Settings.EXPORTED_FUNCTIONS += ['_memalign']

      # dynCall is used to call pthread entry points in worker.js (as
      # metadce does not consider worker.js, which is external, we must
      # consider it an export, i.e., one which can never be removed).
      shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$dynCall']
      shared.Settings.EXPORTED_FUNCTIONS += ['dynCall']

      if shared.Settings.MINIMAL_RUNTIME:
        building.user_requested_exports += ['exit']

      if shared.Settings.PROXY_TO_PTHREAD:
        shared.Settings.EXPORTED_FUNCTIONS += ['_proxy_main']

      # pthread stack setup and other necessary utilities
      def include_and_export(name):
        shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$' + name]
        shared.Settings.EXPORTED_FUNCTIONS += [name]

      include_and_export('establishStackSpace')
      if not shared.Settings.MINIMAL_RUNTIME:
        # noExitRuntime does not apply to MINIMAL_RUNTIME.
        include_and_export('getNoExitRuntime')

      if shared.Settings.MODULARIZE:
        if shared.Settings.EXPORT_NAME == 'Module':
          exit_with_error('pthreads + MODULARIZE currently require you to set -s EXPORT_NAME=Something (see settings.js) to Something != Module, so that the .worker.js file can work')

        # MODULARIZE+USE_PTHREADS mode requires extra exports out to Module so that worker.js
        # can access them:

        # general threading variables:
        shared.Settings.EXPORTED_RUNTIME_METHODS += ['PThread']

        # To keep code size to minimum, MINIMAL_RUNTIME does not utilize the global ExitStatus
        # object, only regular runtime has it.
        if not shared.Settings.MINIMAL_RUNTIME:
          shared.Settings.EXPORTED_RUNTIME_METHODS += ['ExitStatus']

        # stack check:
        if shared.Settings.STACK_OVERFLOW_CHECK:
          shared.Settings.EXPORTED_RUNTIME_METHODS += ['writeStackCookie', 'checkStackCookie']

      if shared.Settings.LINKABLE:
        exit_with_error('-s LINKABLE=1 is not supported with -s USE_PTHREADS>0!')
      if shared.Settings.SIDE_MODULE:
        exit_with_error('-s SIDE_MODULE=1 is not supported with -s USE_PTHREADS>0!')
      if shared.Settings.MAIN_MODULE:
        exit_with_error('-s MAIN_MODULE=1 is not supported with -s USE_PTHREADS>0!')
      if shared.Settings.PROXY_TO_WORKER:
        exit_with_error('--proxy-to-worker is not supported with -s USE_PTHREADS>0! Use the option -s PROXY_TO_PTHREAD=1 if you want to run the main thread of a multithreaded application in a web worker.')
    else:
      if shared.Settings.PROXY_TO_PTHREAD:
        exit_with_error('-s PROXY_TO_PTHREAD=1 requires -s USE_PTHREADS to work!')

    if shared.Settings.INITIAL_MEMORY % 65536 != 0:
      exit_with_error('For wasm, INITIAL_MEMORY must be a multiple of 64KB, was ' + str(shared.Settings.INITIAL_MEMORY))
    if shared.Settings.INITIAL_MEMORY >= 2 * 1024 * 1024 * 1024:
      exit_with_error('INITIAL_MEMORY must be less than 2GB due to current spec limitations')
    if shared.Settings.INITIAL_MEMORY < shared.Settings.TOTAL_STACK:
      exit_with_error('INITIAL_MEMORY must be larger than TOTAL_STACK, was ' + str(shared.Settings.INITIAL_MEMORY) + ' (TOTAL_STACK=' + str(shared.Settings.TOTAL_STACK) + ')')
    if shared.Settings.MAXIMUM_MEMORY != -1 and shared.Settings.MAXIMUM_MEMORY % 65536 != 0:
      exit_with_error('MAXIMUM_MEMORY must be a multiple of 64KB, was ' + str(shared.Settings.MAXIMUM_MEMORY))
    if shared.Settings.MEMORY_GROWTH_LINEAR_STEP != -1 and shared.Settings.MEMORY_GROWTH_LINEAR_STEP % 65536 != 0:
      exit_with_error('MEMORY_GROWTH_LINEAR_STEP must be a multiple of 64KB, was ' + str(shared.Settings.MEMORY_GROWTH_LINEAR_STEP))
    if shared.Settings.USE_PTHREADS and shared.Settings.ALLOW_MEMORY_GROWTH and shared.Settings.MAXIMUM_MEMORY == -1:
      exit_with_error('If pthreads and memory growth are enabled, MAXIMUM_MEMORY must be set')

    if shared.Settings.EXPORT_ES6 and not shared.Settings.MODULARIZE:
      exit_with_error('EXPORT_ES6 requires MODULARIZE to be set')

    if shared.Settings.MODULARIZE and not shared.Settings.DECLARE_ASM_MODULE_EXPORTS:
      # When MODULARIZE option is used, currently requires declaring all module exports
      # individually - TODO: this could be optimized
      exit_with_error('DECLARE_ASM_MODULE_EXPORTS=0 is not compatible with MODULARIZE')

    # When not declaring asm module exports in outer scope one by one, disable minifying
    # asm.js/wasm module export names so that the names can be passed directly to the outer scope.
    # Also, if using library_exports.js API, disable minification so that the feature can work.
    if not shared.Settings.DECLARE_ASM_MODULE_EXPORTS or 'exports.js' in [x for _, x in libs]:
      shared.Settings.MINIFY_ASMJS_EXPORT_NAMES = 0

    # Enable minification of wasm imports and exports when appropriate, if we
    # are emitting an optimized JS+wasm combo (then the JS knows how to load the minified names).
    # Things that process the JS after this operation would be done must disable this.
    # For example, ASYNCIFY_LAZY_LOAD_CODE needs to identify import names.
    if will_metadce() and \
        shared.Settings.OPT_LEVEL >= 2 and \
        shared.Settings.DEBUG_LEVEL <= 2 and \
        not shared.Settings.LINKABLE and \
        not shared.Settings.STANDALONE_WASM and \
        not shared.Settings.AUTODEBUG and \
        not shared.Settings.ASSERTIONS and \
        not shared.Settings.RELOCATABLE and \
        not target.endswith(WASM_ENDINGS) and \
        not shared.Settings.ASYNCIFY_LAZY_LOAD_CODE and \
            shared.Settings.MINIFY_ASMJS_EXPORT_NAMES:
      shared.Settings.MINIFY_WASM_IMPORTS_AND_EXPORTS = 1
      shared.Settings.MINIFY_WASM_IMPORTED_MODULES = 1

    if shared.Settings.MINIMAL_RUNTIME:
      # Minimal runtime uses a different default shell file
      if options.shell_path == shared.path_from_root('src', 'shell.html'):
        options.shell_path = shared.path_from_root('src', 'shell_minimal_runtime.html')

      if shared.Settings.ASSERTIONS and shared.Settings.MINIMAL_RUNTIME:
        # In ASSERTIONS-builds, functions UTF8ArrayToString() and stringToUTF8Array() (which are not JS library functions), both
        # use warnOnce(), which in MINIMAL_RUNTIME is a JS library function, so explicitly have to mark dependency to warnOnce()
        # in that case. If string functions are turned to library functions in the future, then JS dependency tracking can be
        # used and this special directive can be dropped.
        shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$warnOnce']

      # Require explicit -lfoo.js flags to link with JS libraries.
      shared.Settings.AUTO_JS_LIBRARIES = 0

    if shared.Settings.MODULARIZE and shared.Settings.EXPORT_NAME == 'Module' and final_suffix == '.html' and \
       (options.shell_path == shared.path_from_root('src', 'shell.html') or options.shell_path == shared.path_from_root('src', 'shell_minimal.html')):
      exit_with_error('Due to collision in variable name "Module", the shell file "' + options.shell_path + '" is not compatible with build options "-s MODULARIZE=1 -s EXPORT_NAME=Module". Either provide your own shell file, change the name of the export to something else to avoid the name collision. (see https://github.com/emscripten-core/emscripten/issues/7950 for details)')

    if shared.Settings.STANDALONE_WASM:
      if shared.Settings.USE_PTHREADS:
        exit_with_error('STANDALONE_WASM does not support pthreads yet')
      if shared.Settings.MINIMAL_RUNTIME:
        exit_with_error('MINIMAL_RUNTIME reduces JS size, and is incompatible with STANDALONE_WASM which focuses on ignoring JS anyhow and being 100% wasm')
      # the wasm must be runnable without the JS, so there cannot be anything that
      # requires JS legalization
      shared.Settings.LEGALIZE_JS_FFI = 0

    if shared.Settings.WASM_BIGINT:
      shared.Settings.LEGALIZE_JS_FFI = 0

    if shared.Settings.SINGLE_FILE:
      # placeholder strings for JS glue, to be replaced with subresource locations in do_binaryen
      shared.Settings.WASM_BINARY_FILE = shared.FilenameReplacementStrings.WASM_BINARY_FILE
    else:
      # set file locations, so that JS glue can find what it needs
      shared.Settings.WASM_BINARY_FILE = shared.JS.escape_for_js_string(os.path.basename(wasm_target))
    if options.use_closure_compiler == 2 and not shared.Settings.WASM2JS:
      exit_with_error('closure compiler mode 2 assumes the code is asm.js, so not meaningful for wasm')
    if any(s.startswith('MEM_INIT_METHOD=') for s in settings_changes):
      exit_with_error('MEM_INIT_METHOD is not supported in wasm. Memory will be embedded in the wasm binary if threads are not used, and included in a separate file if threads are used.')
    if shared.Settings.WASM2JS:
      shared.Settings.MAYBE_WASM2JS = 1
      # when using wasm2js, if the memory segments are in the wasm then they
      # end up converted by wasm2js into base64 encoded JS. alternatively, we
      # can use a .mem file like asm.js used to.
      # generally we follow what the options tell us to do (which is to use
      # a .mem file in most cases, since it is binary & compact). however, for
      # pthreads we must keep the memory segments in the wasm as they will be
      # passive segments which the .mem format cannot handle.
      shared.Settings.MEM_INIT_IN_WASM = not options.memory_init_file or shared.Settings.SINGLE_FILE or shared.Settings.USE_PTHREADS
    else:
      # wasm includes the mem init in the wasm binary. The exception is
      # wasm2js, which behaves more like js.
      options.memory_init_file = True
      shared.Settings.MEM_INIT_IN_WASM = True

    # wasm side modules have suffix .wasm
    if shared.Settings.SIDE_MODULE and target.endswith('.js'):
      diagnostics.warning('emcc', 'output suffix .js requested, but wasm side modules are just wasm files; emitting only a .wasm, no .js')

    sanitize = set()

    for arg in newargs:
      if arg.startswith('-fsanitize='):
        sanitize.update(arg.split('=', 1)[1].split(','))
      elif arg.startswith('-fno-sanitize='):
        sanitize.difference_update(arg.split('=', 1)[1].split(','))

    if sanitize:
      shared.Settings.USE_OFFSET_CONVERTER = 1
      shared.Settings.EXPORTED_FUNCTIONS += [
          '_memalign',
          '_emscripten_builtin_memalign',
          '_emscripten_builtin_malloc',
          '_emscripten_builtin_free',
          '___data_end',
          '___heap_base',
          '___global_base'
      ]

    if sanitize & UBSAN_SANITIZERS:
      if '-fsanitize-minimal-runtime' in newargs:
        shared.Settings.UBSAN_RUNTIME = 1
      else:
        shared.Settings.UBSAN_RUNTIME = 2

    if 'leak' in sanitize:
      shared.Settings.USE_LSAN = 1
      shared.Settings.EXIT_RUNTIME = 1

      if shared.Settings.LINKABLE:
        exit_with_error('LSan does not support dynamic linking')

    if 'address' in sanitize:
      shared.Settings.USE_ASAN = 1
      if not shared.Settings.UBSAN_RUNTIME:
        shared.Settings.UBSAN_RUNTIME = 2

      shared.Settings.EXPORTED_FUNCTIONS += [
        '_emscripten_builtin_memset',
        '_asan_c_load_1', '_asan_c_load_1u',
        '_asan_c_load_2', '_asan_c_load_2u',
        '_asan_c_load_4', '_asan_c_load_4u',
        '_asan_c_load_f', '_asan_c_load_d',
        '_asan_c_store_1', '_asan_c_store_1u',
        '_asan_c_store_2', '_asan_c_store_2u',
        '_asan_c_store_4', '_asan_c_store_4u',
        '_asan_c_store_f', '_asan_c_store_d',
      ]

      if shared.Settings.ASAN_SHADOW_SIZE != -1:
        diagnostics.warning('emcc', 'ASAN_SHADOW_SIZE is ignored and will be removed in a future release')

      if shared.Settings.GLOBAL_BASE != -1:
        exit_with_error("ASan does not support custom GLOBAL_BASE")

      max_mem = shared.Settings.INITIAL_MEMORY
      if shared.Settings.ALLOW_MEMORY_GROWTH:
        max_mem = shared.Settings.MAXIMUM_MEMORY
        if max_mem == -1:
          exit_with_error('ASan requires a finite MAXIMUM_MEMORY')

      shadow_size = max_mem // 8
      shared.Settings.GLOBAL_BASE = shadow_size

      if shared.Settings.SAFE_HEAP:
        # SAFE_HEAP instruments ASan's shadow memory accesses.
        # Since the shadow memory starts at 0, the act of accessing the shadow memory is detected
        # by SAFE_HEAP as a null pointer dereference.
        exit_with_error('ASan does not work with SAFE_HEAP')

      if shared.Settings.LINKABLE:
        exit_with_error('ASan does not support dynamic linking')

    if sanitize and '-g4' in args:
      shared.Settings.LOAD_SOURCE_MAP = 1

    if shared.Settings.GLOBAL_BASE == -1:
      # default if nothing else sets it
      # a higher global base is useful for optimizing load/store offsets, as it
      # enables the --post-emscripten pass
      shared.Settings.GLOBAL_BASE = 1024

    # various settings require malloc/free support from JS
    if shared.Settings.RELOCATABLE or \
       shared.Settings.BUILD_AS_WORKER or \
       shared.Settings.USE_WEBGPU or \
       shared.Settings.USE_PTHREADS or \
       shared.Settings.OFFSCREENCANVAS_SUPPORT or \
       shared.Settings.LEGACY_GL_EMULATION or \
       shared.Settings.DISABLE_EXCEPTION_CATCHING != 1 or \
       shared.Settings.ASYNCIFY or \
       shared.Settings.ASMFS or \
       shared.Settings.DEMANGLE_SUPPORT or \
       shared.Settings.FORCE_FILESYSTEM or \
       shared.Settings.STB_IMAGE or \
       shared.Settings.EMBIND or \
       shared.Settings.FETCH or \
       shared.Settings.PROXY_POSIX_SOCKETS or \
       options.memory_profiler or \
       sanitize:
      shared.Settings.EXPORTED_FUNCTIONS += ['_malloc', '_free']

    options.binaryen_passes += backend_binaryen_passes()

    if shared.Settings.WASM2JS and use_source_map():
      exit_with_error('wasm2js does not support source maps yet (debug in wasm for now)')

    if shared.Settings.NODE_CODE_CACHING:
      if shared.Settings.WASM_ASYNC_COMPILATION:
        exit_with_error('NODE_CODE_CACHING requires sync compilation (WASM_ASYNC_COMPILATION=0)')
      if not shared.Settings.target_environment_may_be('node'):
        exit_with_error('NODE_CODE_CACHING only works in node, but target environments do not include it')
      if shared.Settings.SINGLE_FILE:
        exit_with_error('NODE_CODE_CACHING saves a file on the side and is not compatible with SINGLE_FILE')

    if options.tracing:
      cflags.append('-D__EMSCRIPTEN_TRACING__=1')
      if shared.Settings.ALLOW_MEMORY_GROWTH:
        shared.Settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['emscripten_trace_report_memory_layout']

    if shared.Settings.USE_PTHREADS:
      newargs.append('-pthread')

    # check if we can address the 2GB mark and higher: either if we start at
    # 2GB, or if we allow growth to either any amount or to 2GB or more.
    if shared.Settings.INITIAL_MEMORY > 2 * 1024 * 1024 * 1024 or \
       (shared.Settings.ALLOW_MEMORY_GROWTH and
        (shared.Settings.MAXIMUM_MEMORY < 0 or
         shared.Settings.MAXIMUM_MEMORY > 2 * 1024 * 1024 * 1024)):
      shared.Settings.CAN_ADDRESS_2GB = 1
      if shared.Settings.MALLOC == 'emmalloc':
        if shared.Settings.INITIAL_MEMORY >= 2 * 1024 * 1024 * 1024:
          suggestion = 'decrease INITIAL_MEMORY'
        elif shared.Settings.MAXIMUM_MEMORY < 0:
          suggestion = 'set MAXIMUM_MEMORY'
        else:
          suggestion = 'decrease MAXIMUM_MEMORY'
        exit_with_error('emmalloc only works on <2GB of memory. Use the default allocator, or ' + suggestion)

    shared.Settings.EMSCRIPTEN_VERSION = shared.EMSCRIPTEN_VERSION
    shared.Settings.PROFILING_FUNCS = options.profiling_funcs
    shared.Settings.SOURCE_MAP_BASE = options.source_map_base or ''

    ## Compile source code to bitcode

    logger.debug('compiling to bitcode')

    temp_files = []

  # exit block 'parse arguments and setup'
  log_time('parse arguments and setup')

  if DEBUG:
    # we are about to start using temp dirs. serialize access to the temp dir
    # when using EMCC_DEBUG, since we don't want multiple processes would to
    # use it at once, they might collide if they happen to use the same
    # tempfile names
    shared.Cache.acquire_cache_lock()

  try:
    with ToolchainProfiler.profile_block('compile inputs'):
      def is_link_flag(flag):
        if flag.startswith('-nostdlib'):
          return True
        return flag.startswith(('-l', '-L', '-Wl,'))

      compile_args = [a for a in newargs if a and not is_link_flag(a)]

      if not building.can_inline():
        cflags.append('-fno-inline-functions')

      def use_cxx(src):
        if 'c++' in language_mode or run_via_emxx:
          return True
        # Next consider the filename
        if src.endswith(C_ENDINGS + OBJC_ENDINGS):
          return False
        if src.endswith(CXX_ENDINGS):
          return True
        # Finally fall back to the default
        if shared.Settings.DEFAULT_TO_CXX:
          # Default to using C++ even when run as `emcc`.
          # This means that emcc will act as a C++ linker when no source files are
          # specified.
          # This differs to clang and gcc where the default is always C unless run as
          # clang++/g++.
          return True
        return False

      def get_compiler(cxx):
        if cxx:
          return CXX
        return CC

      def get_clang_command(src_file):
        cxx = use_cxx(src_file)
        base_cflags = shared.get_cflags(args, cxx)
        cmd = get_compiler(cxx) + base_cflags + cflags + compile_args + [src_file]
        return system_libs.process_args(cmd, shared.Settings)

      def get_clang_command_asm(src_file):
        asflags = shared.get_asmflags()
        return get_compiler(use_cxx(src_file)) + asflags + compile_args + [src_file]

      # preprocessor-only (-E) support
      if has_dash_E or '-M' in newargs or '-MM' in newargs or '-fsyntax-only' in newargs:
        for input_file in [x[1] for x in input_files]:
          cmd = get_clang_command(input_file)
          if specified_target:
            cmd += ['-o', specified_target]
          # Do not compile, but just output the result from preprocessing stage or
          # output the dependency rule. Warning: clang and gcc behave differently
          # with -MF! (clang seems to not recognize it)
          logger.debug(('just preprocessor ' if has_dash_E else 'just dependencies: ') + ' '.join(cmd))
          shared.print_compiler_stage(cmd)
          rtn = run_process(cmd, check=False).returncode
          if rtn:
            return rtn
        return 0

      # Precompiled headers support
      if has_header_inputs:
        headers = [header for _, header in input_files]
        for header in headers:
          if not header.endswith(HEADER_ENDINGS):
            exit_with_error('cannot mix precompile headers with non-header inputs: ' + str(headers) + ' : ' + header)
          cxx = use_cxx(header)
          base_cflags = shared.get_cflags(args, cxx)
          cmd = get_compiler(cxx) + base_cflags + cflags + compile_args + [header]
          if specified_target:
            cmd += ['-o', specified_target]
          cmd = system_libs.process_args(cmd, shared.Settings)
          logger.debug("running (for precompiled headers): " + cmd[0] + ' ' + ' '.join(cmd[1:]))
          shared.print_compiler_stage(cmd)
          return run_process(cmd, check=False).returncode

      def get_object_filename(input_file):
        if compile_only and len(input_files) == 1:
          # no need for a temp file, just emit to the right place
          if specified_target:
            return specified_target
          else:
            return unsuffixed_basename(input_files[0][1]) + options.default_object_extension
        else:
          return in_temp(unsuffixed(uniquename(input_file)) + options.default_object_extension)

      def compile_source_file(i, input_file):
        logger.debug('compiling source file: ' + input_file)
        output_file = get_object_filename(input_file)
        temp_files.append((i, output_file))
        if get_file_suffix(input_file) in ASSEMBLY_ENDINGS:
          cmd = get_clang_command_asm(input_file)
        else:
          cmd = get_clang_command(input_file)
        cmd += ['-c', '-o', output_file]
        if shared.Settings.RELOCATABLE:
          cmd.append('-fPIC')
          cmd.append('-fvisibility=default')
        if shared.Settings.LTO:
          cmd.append('-flto=' + shared.Settings.LTO)
        else:
          # With LTO mode these args get passed instead
          # at link time when the backend runs.
          for a in building.llvm_backend_args():
            cmd += ['-mllvm', a]
        shared.print_compiler_stage(cmd)
        shared.check_call(cmd)
        if output_file not in ('-', os.devnull):
          assert(os.path.exists(output_file))

      # First, generate LLVM bitcode. For each input file, we get base.o with bitcode
      for i, input_file in input_files:
        file_suffix = get_file_suffix(input_file)
        if file_suffix in SOURCE_ENDINGS + ASSEMBLY_ENDINGS or (has_dash_c and file_suffix == '.bc'):
          compile_source_file(i, input_file)
        elif file_suffix in DYNAMICLIB_ENDINGS:
          logger.debug('using shared library: ' + input_file)
          temp_files.append((i, input_file))
        elif building.is_ar(input_file):
          logger.debug('using static library: ' + input_file)
          ensure_archive_index(input_file)
          temp_files.append((i, input_file))
        elif language_mode:
          compile_source_file(i, input_file)
        elif input_file == '-':
          exit_with_error('-E or -x required when input is from standard input')
        else:
          # Default to assuming the inputs are object files and pass them to the linker
          logger.debug('using object file: ' + input_file)
          temp_files.append((i, input_file))

    # exit block 'compile inputs'
    log_time('compile inputs')

    with ToolchainProfiler.profile_block('process inputs'):
      # If we were just compiling stop here
      if compile_only:
        if not specified_target:
          assert len(temp_files) == len(input_files)
          for tempf, inputf in zip(temp_files, input_files):
            safe_move(tempf[1], unsuffixed_basename(inputf[1]) + final_suffix)
        else:
          # Specifying -o with multiple input source files is not allowed.
          # We error out much earlier in this case.
          assert len(input_files) == 1
          input_file = input_files[0][1]
          temp_file = temp_files[0][1]
          if specified_target != '-':
            if temp_file != input_file:
              safe_move(temp_file, specified_target)
            else:
              safe_copy(temp_file, specified_target)
          temp_output_base = unsuffixed(temp_file)
          if os.path.exists(temp_output_base + '.d'):
            # There was a .d file generated, from -MD or -MMD and friends, save a copy of it to where the output resides,
            # adjusting the target name away from the temporary file name to the specified target.
            # It will be deleted with the rest of the temporary directory.
            deps = open(temp_output_base + '.d').read()
            deps = deps.replace(temp_output_base + options.default_object_extension, specified_target)
            with open(os.path.join(os.path.dirname(specified_target), os.path.basename(unsuffixed(input_file) + '.d')), "w") as out_dep:
              out_dep.write(deps)

    # exit block 'process inputs'
    log_time('process inputs')

    if compile_only:
      logger.debug('stopping after compile phase')
      for flag in link_flags:
        diagnostics.warning('unused-command-line-argument', "argument unused during compilation: '%s'" % flag[1])
      return 0

    if specified_target and specified_target.startswith('-'):
      exit_with_error('invalid output filename: `%s`' % specified_target)

    using_lld = not (link_to_object and shared.Settings.LTO)
    link_flags = filter_link_flags(link_flags, using_lld)

    # Decide what we will link
    consumed = process_libraries(libs, lib_dirs, temp_files)
    # Filter out libraries that are actually JS libs
    link_flags = [l for l in link_flags if l[0] not in consumed]
    temp_files = filter_out_dynamic_libs(temp_files)

    linker_inputs = [val for _, val in sorted(temp_files + link_flags)]

    if link_to_object:
      with ToolchainProfiler.profile_block('linking to object file'):
        logger.debug('link_to_object: ' + str(linker_inputs) + ' -> ' + target)
        if len(temp_files) == 1:
          temp_file = temp_files[0][1]
          # skip running the linker and just copy the object file
          safe_copy(temp_file, target)
        else:
          building.link_to_object(linker_inputs, target)
        logger.debug('stopping after linking to object file')
        return 0

    if final_suffix in ('.o', '.bc', '.so', '.dylib') and not shared.Settings.SIDE_MODULE:
     diagnostics.warning('emcc', 'generating an executable with an object extension (%s).  If you meant to build an object file please use `-c, `-r`, or `-shared`' % final_suffix)

    ## Continue on to create JavaScript

    with ToolchainProfiler.profile_block('calculate system libraries'):
      # link in ports and system libraries, if necessary
      if not shared.Settings.SIDE_MODULE: # shared libraries/side modules link no C libraries, need them in parent
        extra_files_to_link = system_libs.get_ports(shared.Settings)
        if '-nostdlib' not in newargs and '-nodefaultlibs' not in newargs:
          link_as_cxx = run_via_emxx
          # Traditionally we always link as C++.  For compatibility we continue to do that,
          # unless running in strict mode.
          if not shared.Settings.STRICT and '-nostdlib++' not in newargs:
            link_as_cxx = True
          extra_files_to_link += system_libs.calculate([f for _, f in sorted(temp_files)] + extra_files_to_link, link_as_cxx, forced=forced_stdlibs)
        linker_inputs += extra_files_to_link

    # exit block 'calculate system libraries'
    log_time('calculate system libraries')

    def dedup_list(lst):
      rtn = []
      for item in lst:
        if item not in rtn:
          rtn.append(item)
      return rtn

    # Make a final pass over shared.Settings.EXPORTED_FUNCTIONS to remove any
    # duplication between functions added by the driver/libraries and function
    # specified by the user
    shared.Settings.EXPORTED_FUNCTIONS = dedup_list(shared.Settings.EXPORTED_FUNCTIONS)

    with ToolchainProfiler.profile_block('link'):
      logger.debug('linking: ' + str(linker_inputs))
      tmp_wasm = in_temp(target_basename + '.wasm')

      # if  EMCC_DEBUG=2  then we must link now, so the temp files are complete.
      # if using the wasm backend, we might be using vanilla LLVM, which does not allow our
      # fastcomp deferred linking opts.
      # TODO: we could check if this is a fastcomp build, and still speed things up here
      js_funcs = None
      if shared.Settings.LLD_REPORT_UNDEFINED and shared.Settings.ERROR_ON_UNDEFINED_SYMBOLS:
        js_funcs = get_all_js_syms(misc_temp_files)
        log_time('JS symbol generation')
      building.link_lld(linker_inputs, tmp_wasm, external_symbol_list=js_funcs)
      # Special handling for when the user passed '-Wl,--version'.  In this case the linker
      # does not create the output file, but just prints its version and exits with 0.
      if '--version' in linker_inputs:
        return 0

    # exit block 'link'
    log_time('link')

    if target == os.devnull:
      # TODO(sbc): In theory we should really run the whole pipeline even if the output is
      # /dev/null, but that will take some refactoring
      return 0

    wasm_only = shared.Settings.SIDE_MODULE or final_suffix in WASM_ENDINGS

    with ToolchainProfiler.profile_block('emscript'):
      # Emscripten
      logger.debug('LLVM => JS')
      if options.memory_init_file:
        shared.Settings.MEM_INIT_METHOD = 1
      else:
        assert shared.Settings.MEM_INIT_METHOD != 1

      if embed_memfile():
        shared.Settings.SUPPORT_BASE64_EMBEDDING = 1

      if wasm_only:
        final_js = None
      else:
        final_js = tmp_wasm + '.js'
      emscripten.run(tmp_wasm, final_js, shared.replace_or_append_suffix(target, '.mem'))

      save_intermediate('original')

      # we also received the wasm at this stage
      safe_move(tmp_wasm, wasm_target)
      if use_source_map():
        safe_move(tmp_wasm + '.map', wasm_source_map_target)

    # exit block 'emscript'
    log_time('emscript (llvm => executable code)')

    with ToolchainProfiler.profile_block('source transforms'):
      # Embed and preload files
      if len(options.preload_files) or len(options.embed_files):
        logger.debug('setting up files')
        file_args = ['--from-emcc', '--export-name=' + shared.Settings.EXPORT_NAME]
        if len(options.preload_files):
          file_args.append('--preload')
          file_args += options.preload_files
        if len(options.embed_files):
          file_args.append('--embed')
          file_args += options.embed_files
        if len(options.exclude_files):
          file_args.append('--exclude')
          file_args += options.exclude_files
        if options.use_preload_cache:
          file_args.append('--use-preload-cache')
        if shared.Settings.LZ4:
          file_args.append('--lz4')
        if options.use_preload_plugins:
          file_args.append('--use-preload-plugins')
        file_code = shared.check_call([shared.PYTHON, shared.FILE_PACKAGER, unsuffixed(target) + '.data'] + file_args, stdout=PIPE).stdout
        options.pre_js = js_manipulation.add_files_pre_js(options.pre_js, file_code)

      # Apply pre and postjs files
      if final_js and (options.pre_js or options.post_js):
        logger.debug('applying pre/postjses')
        src = open(final_js).read()
        final_js += '.pp.js'
        with open(final_js, 'w') as f:
          # pre-js code goes right after the Module integration code (so it
          # can use Module), we have a marker for it
          f.write(src.replace('// {{PRE_JSES}}', fix_windows_newlines(options.pre_js)))
          f.write(fix_windows_newlines(options.post_js))
        options.pre_js = src = options.post_js = None
        save_intermediate('pre-post')

      # Apply a source code transformation, if requested
      if options.js_transform:
        safe_copy(final_js, final_js + '.tr.js')
        final_js += '.tr.js'
        posix = not shared.WINDOWS
        logger.debug('applying transform: %s', options.js_transform)
        shared.check_call(building.remove_quotes(shlex.split(options.js_transform, posix=posix) + [os.path.abspath(final_js)]))
        save_intermediate('transformed')

    # exit block 'source transforms'
    log_time('source transforms')

    with ToolchainProfiler.profile_block('memory initializer'):
      memfile = None
      if not shared.Settings.MEM_INIT_IN_WASM:
         memfile = shared.replace_or_append_suffix(target, '.mem')
      if memfile:
        # For the wasm backend, we don't have any memory info in JS. All we need to do
        # is set the memory initializer url.
        src = open(final_js).read()
        src = src.replace('var memoryInitializer = null;', 'var memoryInitializer = "%s";' % os.path.basename(memfile))
        open(final_js + '.mem.js', 'w').write(src)
        final_js += '.mem.js'

    log_time('memory initializer')

    with ToolchainProfiler.profile_block('binaryen'):
      do_binaryen(target, options, wasm_target)

    log_time('binaryen')
    # If we are not emitting any JS then we are all done now
    if wasm_only:
      return

    with ToolchainProfiler.profile_block('final emitting'):
      # Remove some trivial whitespace
      # TODO: do not run when compress has already been done on all parts of the code
      # src = open(final_js).read()
      # src = re.sub(r'\n+[ \n]*\n+', '\n', src)
      # open(final_js, 'w').write(src)

      if shared.Settings.USE_PTHREADS:
        target_dir = os.path.dirname(os.path.abspath(target))
        worker_output = os.path.join(target_dir, shared.Settings.PTHREAD_WORKER_FILE)
        with open(worker_output, 'w') as f:
          f.write(shared.read_and_preprocess(shared.path_from_root('src', 'worker.js'), expand_macros=True))

        # Minify the worker.js file in optimized builds
        if (shared.Settings.OPT_LEVEL >= 1 or shared.Settings.SHRINK_LEVEL >= 1) and not shared.Settings.DEBUG_LEVEL:
          minified_worker = building.acorn_optimizer(worker_output, ['minifyWhitespace'], return_output=True)
          open(worker_output, 'w').write(minified_worker)

      # track files that will need native eols
      generated_text_files_with_native_eols = []

      if shared.Settings.MODULARIZE:
        modularize()

      module_export_name_substitution()

      # Run a final regex pass to clean up items that were not possible to optimize by Closure, or unoptimalities that were left behind
      # by processing steps that occurred after Closure.
      if shared.Settings.MINIMAL_RUNTIME == 2 and shared.Settings.USE_CLOSURE_COMPILER and shared.Settings.DEBUG_LEVEL == 0 and not shared.Settings.SINGLE_FILE:
        # Process .js runtime file. Note that we need to handle the license text
        # here, so that it will not confuse the hacky script.
        shared.JS.handle_license(final_js)
        shared.run_process([shared.PYTHON, shared.path_from_root('tools', 'hacky_postprocess_around_closure_limitations.py'), final_js])

      # Apply pre and postjs files
      if options.extern_pre_js or options.extern_post_js:
        logger.debug('applying extern pre/postjses')
        src = open(final_js).read()
        final_js += '.epp.js'
        with open(final_js, 'w') as f:
          f.write(fix_windows_newlines(options.extern_pre_js))
          f.write(src)
          f.write(fix_windows_newlines(options.extern_post_js))
        save_intermediate('extern-pre-post')

      shared.JS.handle_license(final_js)

      if final_suffix in JS_ENDINGS:
        js_target = target
      else:
        js_target = unsuffixed(target) + '.js'

      # The JS is now final. Move it to its final location
      safe_move(final_js, js_target)

      if not shared.Settings.SINGLE_FILE:
        generated_text_files_with_native_eols += [js_target]

      # If we were asked to also generate HTML, do that
      if final_suffix == '.html':
        generate_html(target, options, js_target, target_basename,
                      wasm_target, memfile)
      else:
        if options.proxy_to_worker:
          generate_worker_js(target, js_target, target_basename)

      if embed_memfile() and memfile:
        shared.try_delete(memfile)

      for f in generated_text_files_with_native_eols:
        tools.line_endings.convert_line_endings_in_file(f, os.linesep, options.output_eol)

      if make_output_executable:
        make_js_executable(js_target)

    log_time('final emitting')
    # exit block 'final emitting'

  finally:
    if DEBUG:
      shared.Cache.release_cache_lock()

  if DEBUG:
    logger.debug('total time: %.2f seconds', (time.time() - start_time))

  return 0


def parse_args(newargs):
  options = EmccOptions()
  settings_changes = []
  user_js_defines = []
  should_exit = False
  eh_enabled = False
  wasm_eh_enabled = False

  for i in range(len(newargs)):
    # On Windows Vista (and possibly others), excessive spaces in the command line
    # leak into the items in this array, so trim e.g. 'foo.cpp ' -> 'foo.cpp'
    newargs[i] = newargs[i].strip()
    arg = newargs[i]

    def check_arg(value):
      if arg.startswith(value) and '=' in arg:
        exit_with_error('Invalid parameter (do not use "=" with "--" options)')
      return arg == value

    def consume_arg():
      # Consume that option and its argument
      if len(newargs) <= i + 1:
        exit_with_error("option '%s' requires an argument" % arg)
      ret = newargs[i + 1]
      newargs[i] = ''
      newargs[i + 1] = ''
      return ret

    if newargs[i].startswith('-O'):
      # Let -O default to -O2, which is what gcc does.
      options.requested_level = newargs[i][2:] or '2'
      if options.requested_level == 's':
        options.llvm_opts = ['-Os']
        options.requested_level = 2
        shared.Settings.SHRINK_LEVEL = 1
        settings_changes.append('INLINING_LIMIT=50')
      elif options.requested_level == 'z':
        options.llvm_opts = ['-Oz']
        options.requested_level = 2
        shared.Settings.SHRINK_LEVEL = 2
        settings_changes.append('INLINING_LIMIT=25')
      shared.Settings.OPT_LEVEL = validate_arg_level(options.requested_level, 3, 'Invalid optimization level: ' + newargs[i], clamp=True)
    elif check_arg('--js-opts'):
      logger.warning('--js-opts ignored when using llvm backend')
      consume_arg()
    elif check_arg('--llvm-opts'):
      options.llvm_opts = parse_value(consume_arg())
    elif newargs[i].startswith('-flto'):
      if '=' in newargs[i]:
        shared.Settings.LTO = newargs[i].split('=')[1]
      else:
        shared.Settings.LTO = "full"
    elif check_arg('--llvm-lto'):
      logger.warning('--llvm-lto ignored when using llvm backend')
      consume_arg()
    elif check_arg('--closure-args'):
      args = consume_arg()
      options.closure_args += shlex.split(args)
    elif check_arg('--closure'):
      options.use_closure_compiler = int(consume_arg())
    elif check_arg('--js-transform'):
      options.js_transform = consume_arg()
    elif check_arg('--pre-js'):
      options.pre_js += open(consume_arg()).read() + '\n'
    elif check_arg('--post-js'):
      options.post_js += open(consume_arg()).read() + '\n'
    elif check_arg('--extern-pre-js'):
      options.extern_pre_js += open(consume_arg()).read() + '\n'
    elif check_arg('--extern-post-js'):
      options.extern_post_js += open(consume_arg()).read() + '\n'
    elif check_arg('--minify'):
      arg = consume_arg()
      if arg != '0':
        exit_with_error('0 is the only supported option for --minify; 1 has been deprecated')
      shared.Settings.DEBUG_LEVEL = max(1, shared.Settings.DEBUG_LEVEL)
    elif newargs[i].startswith('-g'):
      options.requested_debug = newargs[i]
      requested_level = newargs[i][2:] or '3'
      if is_int(requested_level):
        # the -gX value is the debug level (-g1, -g2, etc.)
        shared.Settings.DEBUG_LEVEL = validate_arg_level(requested_level, 4, 'Invalid debug level: ' + newargs[i])
        # if we don't need to preserve LLVM debug info, do not keep this flag
        # for clang
        if shared.Settings.DEBUG_LEVEL < 3:
          newargs[i] = ''
        else:
          # for 3+, report -g to clang as -g4 is not accepted
          newargs[i] = '-g'
      else:
        if requested_level.startswith('force_dwarf'):
          exit_with_error('gforce_dwarf was a temporary option and is no longer necessary (use -g)')
        elif requested_level.startswith('separate-dwarf'):
          # emit full DWARF but also emit it in a file on the side
          newargs[i] = '-g'
          # if a file is provided, use that; otherwise use the default location
          # (note that we do not know the default location until all args have
          # been parsed, so just note True for now).
          if requested_level != 'separate-dwarf':
            if not requested_level.startswith('separate-dwarf=') or requested_level.count('=') != 1:
              exit_with_error('invalid -gseparate-dwarf=FILENAME notation')
            shared.Settings.SEPARATE_DWARF = requested_level.split('=')[1]
          else:
            shared.Settings.SEPARATE_DWARF = True
        # a non-integer level can be something like -gline-tables-only. keep
        # the flag for the clang frontend to emit the appropriate DWARF info.
        # set the emscripten debug level to 3 so that we do not remove that
        # debug info during link (during compile, this does not make a
        # difference).
        shared.Settings.DEBUG_LEVEL = 3
    elif newargs[i] == '-profiling' or newargs[i] == '--profiling':
      shared.Settings.DEBUG_LEVEL = max(shared.Settings.DEBUG_LEVEL, 2)
      options.profiling = True
      newargs[i] = ''
    elif newargs[i] == '-profiling-funcs' or newargs[i] == '--profiling-funcs':
      options.profiling_funcs = True
      newargs[i] = ''
    elif newargs[i] == '--tracing' or newargs[i] == '--memoryprofiler':
      if newargs[i] == '--memoryprofiler':
        options.memory_profiler = True
      options.tracing = True
      newargs[i] = ''
      settings_changes.append("EMSCRIPTEN_TRACING=1")
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'library_trace.js')))
    elif newargs[i] == '--emit-symbol-map':
      options.emit_symbol_map = True
      shared.Settings.EMIT_SYMBOL_MAP = 1
      newargs[i] = ''
    elif newargs[i] == '--bind':
      shared.Settings.EMBIND = 1
      newargs[i] = ''
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'embind', 'emval.js')))
      shared.Settings.SYSTEM_JS_LIBRARIES.append((0, shared.path_from_root('src', 'embind', 'embind.js')))
    elif check_arg('--embed-file'):
      options.embed_files.append(consume_arg())
    elif check_arg('--preload-file'):
      options.preload_files.append(consume_arg())
    elif check_arg('--exclude-file'):
      options.exclude_files.append(consume_arg())
    elif newargs[i].startswith('--use-preload-cache'):
      options.use_preload_cache = True
      newargs[i] = ''
    elif newargs[i].startswith('--no-heap-copy'):
      diagnostics.warning('legacy-settings', 'ignoring legacy flag --no-heap-copy (that is the only mode supported now)')
      newargs[i] = ''
    elif newargs[i].startswith('--use-preload-plugins'):
      options.use_preload_plugins = True
      newargs[i] = ''
    elif newargs[i] == '--ignore-dynamic-linking':
      options.ignore_dynamic_linking = True
      newargs[i] = ''
    elif newargs[i] == '-v':
      shared.PRINT_STAGES = True
      shared.check_sanity(force=True)
    elif check_arg('--shell-file'):
      options.shell_path = consume_arg()
    elif check_arg('--source-map-base'):
      options.source_map_base = consume_arg()
    elif newargs[i] == '--no-entry':
      options.no_entry = True
      newargs[i] = ''
    elif check_arg('--js-library'):
      shared.Settings.SYSTEM_JS_LIBRARIES.append((i + 1, os.path.abspath(consume_arg())))
    elif newargs[i] == '--remove-duplicates':
      diagnostics.warning('legacy-settings', '--remove-duplicates is deprecated as it is no longer needed. If you cannot link without it, file a bug with a testcase')
      newargs[i] = ''
    elif newargs[i] == '--jcache':
      logger.error('jcache is no longer supported')
      newargs[i] = ''
    elif newargs[i] == '--clear-cache':
      logger.info('clearing cache as requested by --clear-cache')
      shared.Cache.erase()
      shared.check_sanity(force=True) # this is a good time for a sanity check
      should_exit = True
    elif newargs[i] == '--clear-ports':
      logger.info('clearing ports and cache as requested by --clear-ports')
      system_libs.Ports.erase()
      shared.Cache.erase()
      shared.check_sanity(force=True) # this is a good time for a sanity check
      should_exit = True
    elif newargs[i] == '--show-ports':
      system_libs.show_ports()
      should_exit = True
    elif check_arg('--memory-init-file'):
      options.memory_init_file = int(consume_arg())
    elif newargs[i] == '--proxy-to-worker':
      options.proxy_to_worker = True
      newargs[i] = ''
    elif newargs[i] == '--valid-abspath':
      options.valid_abspaths.append(newargs[i + 1])
      newargs[i] = ''
      newargs[i + 1] = ''
    elif newargs[i] == '--separate-asm':
      exit_with_error('cannot --separate-asm with the wasm backend, since not emitting asm.js')
    elif newargs[i].startswith(('-I', '-L')):
      path_name = newargs[i][2:]
      if os.path.isabs(path_name) and not is_valid_abspath(options, path_name):
        # Of course an absolute path to a non-system-specific library or header
        # is fine, and you can ignore this warning. The danger are system headers
        # that are e.g. x86 specific and nonportable. The emscripten bundled
        # headers are modified to be portable, local system ones are generally not.
        diagnostics.warning(
            'absolute-paths', '-I or -L of an absolute path "' + newargs[i] +
            '" encountered. If this is to a local system header/library, it may '
            'cause problems (local system files make sense for compiling natively '
            'on your system, but not necessarily to JavaScript).')
    elif newargs[i] == '--emrun':
      options.emrun = True
      newargs[i] = ''
    elif newargs[i] == '--cpuprofiler':
      options.cpu_profiler = True
      newargs[i] = ''
    elif newargs[i] == '--threadprofiler':
      options.thread_profiler = True
      settings_changes.append('PTHREADS_PROFILING=1')
      newargs[i] = ''
    elif newargs[i] == '-fno-exceptions':
      shared.Settings.DISABLE_EXCEPTION_CATCHING = 1
      shared.Settings.DISABLE_EXCEPTION_THROWING = 1
      shared.Settings.EXCEPTION_HANDLING = 0
    elif newargs[i] == '-fexceptions':
      eh_enabled = True
    elif newargs[i] == '-fwasm-exceptions':
      wasm_eh_enabled = True
    elif newargs[i] == '-fignore-exceptions':
      shared.Settings.DISABLE_EXCEPTION_CATCHING = 1
    elif newargs[i] == '--default-obj-ext':
      newargs[i] = ''
      options.default_object_extension = newargs[i + 1]
      if not options.default_object_extension.startswith('.'):
        options.default_object_extension = '.' + options.default_object_extension
      newargs[i + 1] = ''
    elif newargs[i].startswith("-fsanitize=cfi"):
      options.cfi = True
    elif newargs[i] == "--output_eol":
      if newargs[i + 1].lower() == 'windows':
        options.output_eol = '\r\n'
      elif newargs[i + 1].lower() == 'linux':
        options.output_eol = '\n'
      else:
        exit_with_error('Invalid value "' + newargs[i + 1] + '" to --output_eol!')
      newargs[i] = ''
      newargs[i + 1] = ''
    elif newargs[i] == '--generate-config':
      optarg = newargs[i + 1]
      path = os.path.expanduser(optarg)
      if os.path.exists(path):
        exit_with_error('File ' + optarg + ' passed to --generate-config already exists!')
      else:
        shared.generate_config(optarg)
      should_exit = True
    # Record USE_PTHREADS setting because it controls whether --shared-memory is passed to lld
    elif newargs[i] == '-pthread':
      settings_changes.append('USE_PTHREADS=1')
    elif newargs[i] in ('-fno-diagnostics-color', '-fdiagnostics-color=never'):
      colored_logger.disable()
      diagnostics.color_enabled = False
    elif newargs[i] == '-fno-rtti':
      shared.Settings.USE_RTTI = 0
    elif newargs[i] == '-frtti':
      shared.Settings.USE_RTTI = 1

    # TODO Currently -fexceptions only means Emscripten EH. Switch to wasm
    # exception handling by default when -fexceptions is given when wasm
    # exception handling becomes stable.
    if wasm_eh_enabled:
      shared.Settings.EXCEPTION_HANDLING = 1
      shared.Settings.DISABLE_EXCEPTION_THROWING = 1
      shared.Settings.DISABLE_EXCEPTION_CATCHING = 1
    elif eh_enabled:
      shared.Settings.EXCEPTION_HANDLING = 0
      shared.Settings.DISABLE_EXCEPTION_THROWING = 0
      shared.Settings.DISABLE_EXCEPTION_CATCHING = 0
    elif newargs[i].startswith('-jsD'):
      key = newargs[i][4:]
      if '=' in key:
        key, value = key.split('=')
      else:
        value = '1'
      if key in shared.Settings.attrs:
        exit_with_error(newargs[i] + ': cannot change built-in settings values with a -jsD directive. Pass -s ' + key + '=' + value + ' instead!')
      user_js_defines += [(key, value)]
      newargs[i] = ''
    elif newargs[i] == '-shared':
      options.shared = True
      newargs[i] = ''
    elif newargs[i] == '-r':
      options.relocatable = True
      newargs[i] = ''

  if should_exit:
    sys.exit(0)

  newargs = [a for a in newargs if a]
  return options, settings_changes, user_js_defines, newargs


def emit_js_source_maps(target, js_transform_tempfiles):
  logger.debug('generating source maps')
  shared.run_js_tool(shared.path_from_root('tools', 'source-maps', 'sourcemapper.js'),
                     js_transform_tempfiles +
                     ['--sourceRoot', os.getcwd(),
                      '--mapFileBaseName', target,
                      '--offset', '0'])


def do_binaryen(target, options, wasm_target):
  global final_js
  logger.debug('using binaryen')
  if use_source_map() and not shared.Settings.SOURCE_MAP_BASE:
    logger.warning("Wasm source map won't be usable in a browser without --source-map-base")
  # whether we need to emit -g (function name debug info) in the final wasm
  debug_info = shared.Settings.DEBUG_LEVEL >= 2 or options.profiling_funcs
  # whether we need to emit -g in the intermediate binaryen invocations (but not necessarily at the very end).
  # this is necessary for emitting a symbol map at the end.
  intermediate_debug_info = bool(debug_info or options.emit_symbol_map or shared.Settings.ASYNCIFY_ONLY or shared.Settings.ASYNCIFY_REMOVE or shared.Settings.ASYNCIFY_ADD)
  # note that wasm-ld can strip DWARF info for us too (--strip-debug), but it
  # also strips the Names section. so to emit just the Names section we don't
  # tell wasm-ld to strip anything, and we do it here.
  strip_debug = shared.Settings.DEBUG_LEVEL < 3
  strip_producers = not shared.Settings.EMIT_PRODUCERS_SECTION
  # run wasm-opt if we have work for it: either passes, or if we are using
  # source maps (which requires some extra processing to keep the source map
  # but remove DWARF)
  if options.binaryen_passes or use_source_map():
    # if we need to strip certain sections, and we have wasm-opt passes
    # to run anyhow, do it with them.
    if strip_debug:
      options.binaryen_passes += ['--strip-debug']
    if strip_producers:
      options.binaryen_passes += ['--strip-producers']
    building.save_intermediate(wasm_target, 'pre-byn.wasm')
    building.run_wasm_opt(wasm_target,
                          wasm_target,
                          args=options.binaryen_passes,
                          debug=intermediate_debug_info)
  else:
    # we are not running wasm-opt. if we need to strip certain sections
    # then do so using llvm-objcopy which is fast and does not rewrite the
    # code (which is better for debug info)
    if strip_debug or strip_producers:
      building.save_intermediate(wasm_target, 'pre-strip.wasm')
      building.strip(wasm_target, wasm_target, debug=strip_debug, producers=strip_producers)

  if shared.Settings.EVAL_CTORS:
    building.save_intermediate(wasm_target, 'pre-ctors.wasm')
    building.eval_ctors(final_js, wasm_target, debug_info=intermediate_debug_info)

  # after generating the wasm, do some final operations
  if shared.Settings.SIDE_MODULE:
    webassembly.add_dylink_section(wasm_target, shared.Settings.RUNTIME_LINKED_LIBS)

  if shared.Settings.EMIT_EMSCRIPTEN_METADATA:
    webassembly.add_emscripten_metadata(wasm_target)

  if final_js:
    # pthreads memory growth requires some additional JS fixups
    if shared.Settings.USE_PTHREADS and shared.Settings.ALLOW_MEMORY_GROWTH:
      final_js = building.apply_wasm_memory_growth(final_js)

    # >=2GB heap support requires pointers in JS to be unsigned. rather than
    # require all pointers to be unsigned by default, which increases code size
    # a little, keep them signed, and just unsign them here if we need that.
    if shared.Settings.CAN_ADDRESS_2GB:
      final_js = building.use_unsigned_pointers_in_js(final_js)

    if shared.Settings.USE_ASAN:
      final_js = building.instrument_js_for_asan(final_js)

    if shared.Settings.SAFE_HEAP:
      final_js = building.instrument_js_for_safe_heap(final_js)

    if shared.Settings.OPT_LEVEL >= 2 and shared.Settings.DEBUG_LEVEL <= 2:
      # minify the JS
      save_intermediate_with_wasm('preclean', wasm_target)
      final_js = building.minify_wasm_js(js_file=final_js,
                                         wasm_file=wasm_target,
                                         expensive_optimizations=will_metadce(),
                                         minify_whitespace=minify_whitespace(),
                                         debug_info=intermediate_debug_info)
      save_intermediate_with_wasm('postclean', wasm_target)

  if shared.Settings.ASYNCIFY_LAZY_LOAD_CODE:
    if not shared.Settings.ASYNCIFY:
      exit_with_error('ASYNCIFY_LAZY_LOAD_CODE requires ASYNCIFY')
    building.asyncify_lazy_load_code(wasm_target, debug=intermediate_debug_info)

  def preprocess_wasm2js_script():
    return read_and_preprocess(shared.path_from_root('src', 'wasm2js.js'), expand_macros=True)

  def run_closure_compiler():
    global final_js
    final_js = building.closure_compiler(final_js, pretty=not minify_whitespace(),
                                         extra_closure_args=options.closure_args)
    save_intermediate_with_wasm('closure', wasm_target)

  if final_js and options.use_closure_compiler:
    run_closure_compiler()

  symbols_file = shared.replace_or_append_suffix(target, '.symbols') if options.emit_symbol_map else None

  if shared.Settings.WASM2JS:
    if shared.Settings.WASM == 2:
      wasm2js_template = wasm_target + '.js'
      open(wasm2js_template, 'w').write(preprocess_wasm2js_script())
    else:
      wasm2js_template = final_js

    wasm2js = building.wasm2js(wasm2js_template,
                               wasm_target,
                               opt_level=shared.Settings.OPT_LEVEL,
                               minify_whitespace=minify_whitespace(),
                               use_closure_compiler=options.use_closure_compiler,
                               debug_info=debug_info,
                               symbols_file=symbols_file)
    if shared.Settings.WASM == 2:
      safe_copy(wasm2js, wasm2js_template)
      shared.try_delete(wasm2js)

    if shared.Settings.WASM != 2:
      final_js = wasm2js
      # if we only target JS, we don't need the wasm any more
      shared.try_delete(wasm_target)

    save_intermediate('wasm2js')

  # emit the final symbols, either in the binary or in a symbol map.
  # this will also remove debug info if we only kept it around in the intermediate invocations.
  # note that if we aren't emitting a binary (like in wasm2js) then we don't
  # have anything to do here.
  if options.emit_symbol_map and os.path.exists(wasm_target):
    building.handle_final_wasm_symbols(wasm_file=wasm_target, symbols_file=symbols_file, debug_info=debug_info)
    save_intermediate_with_wasm('symbolmap', wasm_target)

  if shared.Settings.DEBUG_LEVEL >= 3 and shared.Settings.SEPARATE_DWARF and os.path.exists(wasm_target):
    building.emit_debug_on_side(wasm_target, shared.Settings.SEPARATE_DWARF)

  if shared.Settings.WASM2C:
    wasm2c.do_wasm2c(wasm_target)

  # replace placeholder strings with correct subresource locations
  if final_js and shared.Settings.SINGLE_FILE:
    js = open(final_js).read()

    if '{{{ WASM_BINARY_DATA }}}' in js:
      js = js.replace('{{{ WASM_BINARY_DATA }}}', base64_encode(open(wasm_target, 'rb').read()))

    js = js.replace(shared.FilenameReplacementStrings.WASM_BINARY_FILE, shared.JS.get_subresource_location(wasm_target))
    shared.try_delete(wasm_target)
    with open(final_js, 'w') as f:
      f.write(js)


def modularize():
  global final_js
  logger.debug('Modularizing, assigning to var ' + shared.Settings.EXPORT_NAME)
  src = open(final_js).read()

  return_value = shared.Settings.EXPORT_NAME + '.ready'
  if not shared.Settings.EXPORT_READY_PROMISE:
    return_value = '{}'

  src = '''
function(%(EXPORT_NAME)s) {
  %(EXPORT_NAME)s = %(EXPORT_NAME)s || {};

%(src)s

  return %(return_value)s
}
''' % {
    'EXPORT_NAME': shared.Settings.EXPORT_NAME,
    'src': src,
    'return_value': return_value
  }

  if shared.Settings.MINIMAL_RUNTIME and not shared.Settings.USE_PTHREADS:
    # Single threaded MINIMAL_RUNTIME programs do not need access to
    # document.currentScript, so a simple export declaration is enough.
    src = 'var %s=%s' % (shared.Settings.EXPORT_NAME, src)
  else:
    script_url_node = ""
    # When MODULARIZE this JS may be executed later,
    # after document.currentScript is gone, so we save it.
    # In EXPORT_ES6 + USE_PTHREADS the 'thread' is actually an ES6 module webworker running in strict mode,
    # so doesn't have access to 'document'. In this case use 'import.meta' instead.
    if shared.Settings.EXPORT_ES6 and shared.Settings.USE_ES6_IMPORT_META:
      script_url = "import.meta.url"
    else:
      script_url = "typeof document !== 'undefined' && document.currentScript ? document.currentScript.src : undefined"
      if shared.Settings.target_environment_may_be('node'):
        script_url_node = "if (typeof __filename !== 'undefined') _scriptDir = _scriptDir || __filename;"
    src = '''
var %(EXPORT_NAME)s = (function() {
  var _scriptDir = %(script_url)s;
  %(script_url_node)s
  return (%(src)s);
})();
''' % {
      'EXPORT_NAME': shared.Settings.EXPORT_NAME,
      'script_url': script_url,
      'script_url_node': script_url_node,
      'src': src
    }

  final_js += '.modular.js'
  with open(final_js, 'w') as f:
    f.write(src)

    # Export using a UMD style export, or ES6 exports if selected

    if shared.Settings.EXPORT_ES6:
      f.write('''export default %s;''' % shared.Settings.EXPORT_NAME)
    elif not shared.Settings.MINIMAL_RUNTIME:
      f.write('''if (typeof exports === 'object' && typeof module === 'object')
      module.exports = %(EXPORT_NAME)s;
    else if (typeof define === 'function' && define['amd'])
      define([], function() { return %(EXPORT_NAME)s; });
    else if (typeof exports === 'object')
      exports["%(EXPORT_NAME)s"] = %(EXPORT_NAME)s;
    ''' % {
        'EXPORT_NAME': shared.Settings.EXPORT_NAME
      })

  save_intermediate('modularized')


def module_export_name_substitution():
  global final_js
  logger.debug('Private module export name substitution with ' + shared.Settings.EXPORT_NAME)
  src = open(final_js).read()
  final_js += '.module_export_name_substitution.js'
  if shared.Settings.MINIMAL_RUNTIME:
    # In MINIMAL_RUNTIME the Module object is always present to provide the .asm.js/.wasm content
    replacement = shared.Settings.EXPORT_NAME
  else:
    replacement = "typeof %(EXPORT_NAME)s !== 'undefined' ? %(EXPORT_NAME)s : {}" % {"EXPORT_NAME": shared.Settings.EXPORT_NAME}
  with open(final_js, 'w') as f:
    src = re.sub(r'{\s*[\'"]?__EMSCRIPTEN_PRIVATE_MODULE_EXPORT_NAME_SUBSTITUTION__[\'"]?:\s*1\s*}', replacement, src)
    # For Node.js and other shell environments, create an unminified Module object so that
    # loading external .asm.js file that assigns to Module['asm'] works even when Closure is used.
    if shared.Settings.MINIMAL_RUNTIME and (shared.Settings.target_environment_may_be('node') or shared.Settings.target_environment_may_be('shell')):
      src = 'if(typeof Module==="undefined"){var Module={};}' + src
    f.write(src)
  save_intermediate('module_export_name_substitution')


def generate_traditional_runtime_html(target, options, js_target, target_basename,
                                      wasm_target, memfile):
  script = ScriptSource()

  shell = read_and_preprocess(options.shell_path)
  assert '{{{ SCRIPT }}}' in shell, 'HTML shell must contain  {{{ SCRIPT }}}  , see src/shell.html for an example'
  base_js_target = os.path.basename(js_target)

  if options.proxy_to_worker:
    proxy_worker_filename = (shared.Settings.PROXY_TO_WORKER_FILENAME or target_basename) + '.js'
    worker_js = worker_js_script(proxy_worker_filename)
    script.inline = ('''
  var filename = '%s';
  if ((',' + window.location.search.substr(1) + ',').indexOf(',noProxy,') < 0) {
    console.log('running code in a web worker');
''' % shared.JS.get_subresource_location(proxy_worker_filename)) + worker_js + '''
  } else {
    console.log('running code on the main thread');
    var fileBytes = tryParseAsDataURI(filename);
    var script = document.createElement('script');
    if (fileBytes) {
      script.innerHTML = intArrayToString(fileBytes);
    } else {
      script.src = filename;
    }
    document.body.appendChild(script);
  }
'''
  else:
    # Normal code generation path
    script.src = base_js_target

  if not shared.Settings.SINGLE_FILE:
    if options.memory_init_file and not shared.Settings.MEM_INIT_IN_WASM:
      # start to load the memory init file in the HTML, in parallel with the JS
      script.un_src()
      script.inline = ('''
          var memoryInitializer = '%s';
          memoryInitializer = Module['locateFile'] ? Module['locateFile'](memoryInitializer, '') : memoryInitializer;
          Module['memoryInitializerRequestURL'] = memoryInitializer;
          var meminitXHR = Module['memoryInitializerRequest'] = new XMLHttpRequest();
          meminitXHR.open('GET', memoryInitializer, true);
          meminitXHR.responseType = 'arraybuffer';
          meminitXHR.send(null);
''' % shared.JS.get_subresource_location(memfile)) + script.inline

    if not shared.Settings.WASM_ASYNC_COMPILATION:
      # We need to load the wasm file before anything else, it has to be synchronously ready TODO: optimize
      script.un_src()
      script.inline = '''
          var wasmURL = '%s';
          var wasmXHR = new XMLHttpRequest();
          wasmXHR.open('GET', wasmURL, true);
          wasmXHR.responseType = 'arraybuffer';
          wasmXHR.onload = function() {
            if (wasmXHR.status === 200 || wasmXHR.status === 0) {
              Module.wasmBinary = wasmXHR.response;
            } else {
              var wasmURLBytes = tryParseAsDataURI(wasmURL);
              if (wasmURLBytes) {
                Module.wasmBinary = wasmURLBytes.buffer;
              }
            }
%s
          };
          wasmXHR.send(null);
''' % (shared.JS.get_subresource_location(wasm_target), script.inline)

    if shared.Settings.WASM == 2:
      # If target browser does not support WebAssembly, we need to load the .wasm.js file before the main .js file.
      script.un_src()
      script.inline = '''
          function loadMainJs() {
%s
          }
          if (!window.WebAssembly || location.search.indexOf('_rwasm=0') > 0) {
            // Current browser does not support WebAssembly, load the .wasm.js JavaScript fallback
            // before the main JS runtime.
            var wasm2js = document.createElement('script');
            wasm2js.src = '%s';
            wasm2js.onload = loadMainJs;
            document.body.appendChild(wasm2js);
          } else {
            // Current browser supports Wasm, proceed with loading the main JS runtime.
            loadMainJs();
          }
''' % (script.inline, shared.JS.get_subresource_location(wasm_target) + '.js')

  # when script.inline isn't empty, add required helper functions such as tryParseAsDataURI
  if script.inline:
    for filename in ('arrayUtils.js', 'base64Utils.js', 'URIUtils.js'):
      content = read_and_preprocess(shared.path_from_root('src', filename))
      script.inline = content + script.inline

    script.inline = 'var ASSERTIONS = %s;\n%s' % (shared.Settings.ASSERTIONS, script.inline)

  # inline script for SINGLE_FILE output
  if shared.Settings.SINGLE_FILE:
    js_contents = script.inline or ''
    if script.src:
      js_contents += open(js_target).read()
    shared.try_delete(js_target)
    script.src = None
    script.inline = js_contents

  html_contents = shell.replace('{{{ SCRIPT }}}', script.replacement())
  html_contents = tools.line_endings.convert_line_endings(html_contents, '\n', options.output_eol)
  with open(target, 'wb') as f:
    f.write(asbytes(html_contents))


def minify_html(filename):
  if shared.Settings.DEBUG_LEVEL >= 2:
    return

  opts = []
  # -g1 and greater retain whitespace and comments in source
  if shared.Settings.DEBUG_LEVEL == 0:
    opts += ['--collapse-whitespace',
             '--collapse-inline-tag-whitespace',
             '--remove-comments',
             '--remove-tag-whitespace',
             '--sort-attributes',
             '--sort-class-name']
  # -g2 and greater do not minify HTML at all
  if shared.Settings.DEBUG_LEVEL <= 1:
    opts += ['--decode-entities',
             '--collapse-boolean-attributes',
             '--remove-attribute-quotes',
             '--remove-redundant-attributes',
             '--remove-script-type-attributes',
             '--remove-style-link-type-attributes',
             '--use-short-doctype',
             '--minify-css', 'true',
             '--minify-js', 'true']

  # html-minifier also has the following options, but they look unsafe for use:
  # '--remove-optional-tags': removes e.g. <head></head> and <body></body> tags from the page.
  #                           (Breaks at least browser.test_sdl2glshader)
  # '--remove-empty-attributes': removes all attributes with whitespace-only values.
  #                              (Breaks at least browser.test_asmfs_hello_file)
  # '--remove-empty-elements': removes all elements with empty contents.
  #                            (Breaks at least browser.test_asm_swapping)

  logger.debug('minifying HTML file ' + filename)
  size_before = os.path.getsize(filename)
  start_time = time.time()
  shared.check_call(shared.get_npm_cmd('html-minifier-terser') + [filename, '-o', filename] + opts, env=shared.env_with_node_in_path())

  elapsed_time = time.time() - start_time
  size_after = os.path.getsize(filename)
  delta = size_after - size_before
  logger.debug('HTML minification took {:.2f}'.format(elapsed_time) + ' seconds, and shrunk size of ' + filename + ' from ' + str(size_before) + ' to ' + str(size_after) + ' bytes, delta=' + str(delta) + ' ({:+.2f}%)'.format(delta * 100.0 / size_before))


def generate_html(target, options, js_target, target_basename,
                  wasm_target, memfile):
  logger.debug('generating HTML')

  if shared.Settings.EXPORT_NAME != 'Module' and \
     not shared.Settings.MINIMAL_RUNTIME and \
     options.shell_path == shared.path_from_root('src', 'shell.html'):
    # the minimal runtime shell HTML is designed to support changing the export
    # name, but the normal one does not support that currently
    exit_with_error('Customizing EXPORT_NAME requires that the HTML be customized to use that name (see https://github.com/emscripten-core/emscripten/issues/10086)')

  if shared.Settings.MINIMAL_RUNTIME:
    generate_minimal_runtime_html(target, options, js_target, target_basename)
  else:
    generate_traditional_runtime_html(target, options, js_target, target_basename,
                                      wasm_target, memfile)

  if shared.Settings.MINIFY_HTML and (shared.Settings.OPT_LEVEL >= 1 or shared.Settings.SHRINK_LEVEL >= 1):
    minify_html(target)


def generate_worker_js(target, js_target, target_basename):
  # compiler output is embedded as base64
  if shared.Settings.SINGLE_FILE:
    proxy_worker_filename = shared.JS.get_subresource_location(js_target)

  # compiler output goes in .worker.js file
  else:
    safe_move(js_target, unsuffixed(js_target) + '.worker.js')
    worker_target_basename = target_basename + '.worker'
    proxy_worker_filename = (shared.Settings.PROXY_TO_WORKER_FILENAME or worker_target_basename) + '.js'

  target_contents = worker_js_script(proxy_worker_filename)
  open(target, 'w').write(target_contents)


def worker_js_script(proxy_worker_filename):
  web_gl_client_src = open(shared.path_from_root('src', 'webGLClient.js')).read()
  idb_store_src = open(shared.path_from_root('src', 'IDBStore.js')).read()
  proxy_client_src = (
    open(shared.path_from_root('src', 'proxyClient.js')).read()
    .replace('{{{ filename }}}', proxy_worker_filename)
    .replace('{{{ IDBStore.js }}}', idb_store_src)
  )

  return web_gl_client_src + '\n' + proxy_client_src


def process_libraries(libs, lib_dirs, temp_files):
  libraries = []
  consumed = []

  # Find library files
  for i, lib in libs:
    logger.debug('looking for library "%s"', lib)
    suffixes = list(STATICLIB_ENDINGS + DYNAMICLIB_ENDINGS)

    found = False
    for prefix in LIB_PREFIXES:
      for suff in suffixes:
        name = prefix + lib + suff
        for lib_dir in lib_dirs:
          path = os.path.join(lib_dir, name)
          if os.path.exists(path):
            logger.debug('found library "%s" at %s', lib, path)
            temp_files.append((i, path))
            consumed.append(i)
            found = True
            break
        if found:
          break
      if found:
        break
    if not found:
      jslibs = building.path_to_system_js_libraries(lib)
      if jslibs:
        libraries += [(i, jslib) for jslib in jslibs]
        consumed.append(i)

  shared.Settings.SYSTEM_JS_LIBRARIES += libraries

  # At this point processing SYSTEM_JS_LIBRARIES is finished, no more items will be added to it.
  # Sort the input list from (order, lib_name) pairs to a flat array in the right order.
  shared.Settings.SYSTEM_JS_LIBRARIES.sort(key=lambda lib: lib[0])
  shared.Settings.SYSTEM_JS_LIBRARIES = [lib[1] for lib in shared.Settings.SYSTEM_JS_LIBRARIES]
  return consumed


class ScriptSource(object):
  def __init__(self):
    self.src = None # if set, we have a script to load with a src attribute
    self.inline = None # if set, we have the contents of a script to write inline in a script

  def un_src(self):
    """Use this if you want to modify the script and need it to be inline."""
    if self.src is None:
      return
    self.inline = '''
          var script = document.createElement('script');
          script.src = "%s";
          document.body.appendChild(script);
''' % self.src
    self.src = None

  def replacement(self):
    """Returns the script tag to replace the {{{ SCRIPT }}} tag in the target"""
    assert (self.src or self.inline) and not (self.src and self.inline)
    if self.src:
      return '<script async type="text/javascript" src="%s"></script>' % quote(self.src)
    else:
      return '<script>\n%s\n</script>' % self.inline


def is_valid_abspath(options, path_name):
  # Any path that is underneath the emscripten repository root must be ok.
  if shared.path_from_root().replace('\\', '/') in path_name.replace('\\', '/'):
    return True

  def in_directory(root, child):
    # make both path absolute
    root = os.path.realpath(root)
    child = os.path.realpath(child)

    # return true, if the common prefix of both is equal to directory
    # e.g. /a/b/c/d.rst and directory is /a/b, the common prefix is /a/b
    return os.path.commonprefix([root, child]) == root

  for valid_abspath in options.valid_abspaths:
    if in_directory(valid_abspath, path_name):
      return True
  return False


def parse_value(text):
  if not text:
    return text

  # Note that using response files can introduce whitespace, if the file
  # has a newline at the end. For that reason, we rstrip() in relevant
  # places here.
  def parse_string_value(text):
    first = text[0]
    if first == "'" or first == '"':
      text = text.rstrip()
      assert text[-1] == text[0] and len(text) > 1, 'unclosed opened quoted string. expected final character to be "%s" and length to be greater than 1 in "%s"' % (text[0], text)
      return text[1:-1]
    return text

  def parse_string_list_members(text):
    sep = ','
    values = text.split(sep)
    result = []
    index = 0
    while True:
      current = values[index].lstrip() # Cannot safely rstrip for cases like: "HERE-> ,"
      if not len(current):
        exit_with_error('string array should not contain an empty value')
      first = current[0]
      if not(first == "'" or first == '"'):
        result.append(current.rstrip())
      else:
        start = index
        while True: # Continue until closing quote found
          if index >= len(values):
            exit_with_error("unclosed quoted string. expected final character to be '%s' in '%s'" % (first, values[start]))
          new = values[index].rstrip()
          if new and new[-1] == first:
            if start == index:
              result.append(current.rstrip()[1:-1])
            else:
              result.append((current + sep + new)[1:-1])
            break
          else:
            current += sep + values[index]
            index += 1

      index += 1
      if index >= len(values):
        break
    return result

  def parse_string_list(text):
    text = text.rstrip()
    if text[-1] != ']':
      exit_with_error('unclosed opened string list. expected final character to be "]" in "%s"' % (text))
    inner = text[1:-1]
    if inner.strip() == "":
      return []
    return parse_string_list_members(inner)

  if text[0] == '[':
    # if json parsing fails, we fall back to our own parser, which can handle a few
    # simpler syntaxes
    try:
      return json.loads(text)
    except ValueError:
      return parse_string_list(text)

  try:
    return int(text)
  except ValueError:
    return parse_string_value(text)


def validate_arg_level(level_string, max_level, err_msg, clamp=False):
  try:
    level = int(level_string)
  except ValueError:
    raise Exception(err_msg)
  if clamp:
    if level > max_level:
      logger.warning("optimization level '-O" + level_string + "' is not supported; using '-O" + str(max_level) + "' instead")
      level = max_level
  if not 0 <= level <= max_level:
    raise Exception(err_msg)
  return level


def is_int(s):
  try:
    int(s)
    return True
  except ValueError:
    return False


if __name__ == '__main__':
  try:
    sys.exit(run(sys.argv))
  except KeyboardInterrupt:
    logger.warning('KeyboardInterrupt')
    sys.exit(1)
